Big Gap Hooks
When you’re getting bit, but you need more bite, big-gap hooks do the trick on large trout.
By Scott Sanchez

PMD parachutes. Standard dry fly TMC 100 size 16 and a Fulling Mills Grab Gape size 12. Same length shank different gaps. Which will hold big fish better?

A fly is only as good as the hook. This past spring, I was fishing a trophy trout lake in the Rocky Mountains with a friend, Randolph, and he was getting action, but his standard size-14 nymph hooks were an issue.

The strikes weren’t converting to hook-ups and when he did hook-up, these large fish bent the hook. He asked me, “Are these bad hooks?” I said, “No, size-14 hooks aren’t meant for wrestling large trout on 3X and 2X leaders.”

I gave him some of my shorter shank size-10 and 12 nymphs, which were the same length as the 14. His hook-ups and landings changed big time. That was one example of why tying your lake flies on a bigger gap hook pays dividends. Another occurred at the 2018 Jackson Hole One Fly contest. I tied the winning fly, which was a size-18 Loop Wing Trico that I’d tied on a shorter shank size-16 hook. Greg Case of Team Skwlala caught 47 trout with that single fly—many of them nice size—using 4X leader. The hook didn’t bend and the fly held together. Most size-18 dry-fly hooks would not have handled that workout.

We can use the best materials, execute perfect tying, but if the hook doesn’t function all is lost. I’ve run into many situations when fishing smaller flies where standard premium hooks were not reliable for hooking fish and didn’t have adequate strength. The need for stronger hooks coincides with waters that have larger fish, but require smaller flies. I would say that working on my hook selection for smaller flies has been as important as anything I’ve done in tying.

Olive scud standard nymph hook (bottom) and shorter shank big gap hook. Larger gap will get a better hookup and a more positive hold.

Whether you’re fishing a size- 20 for a 17-inch trout, or a size 10 for a 27-incher, a bigger gap and a shorter shank are desirable assets. Saltwater and big-game anglers have been doing this for years; in my opinion, it’s time trout anglers join in. As a tyer, you have the wonderful option of modifying your flies and it’s time to start doing so, because losing the trout of a lifetime ain’t no fun.

Having strong hooks is emphasized by outrageously strong modern leaders. Advances in copolymer nylons and fluorocarbons keep happening, but with steel hook wire it isn’t so. Where you used to break tippets, now we open hooks.

Open space and mechanics

Probably the simplest way to increase hook-ups and strengthen flies is to tie them on a hook with the shank length we need, but with a bigger gap than we’d typically use. For example, tying a size-16 fly on a shorter shank size-14 hook.

Hooking ability comes down to the gap. You need enough gap for the hook point to extend over fly materials. Soft materials, like marabou or CDC, aren’t much of an issue since they compress and slip out of the way. But the less compressible the material, the more important hook gap is. The biggest culprits are beads. If you want to hook fish, the bead and the hook point need to be separated. On bulky flies, like Chernobyls and hoppers, long-shank hooks work well, but as you shrink flies down, the long hooks are a liability. Mini-Chernobyls and hoppers fish much better on standard-shank or big-gap hooks and they also act as a ballast to make the fly land on the water correctly.

The other factor of gap is a fish’s mouth. Large trout have tough mouths. It is hard to hook big fish on small flies unless you get it perfectly in the corner of the mouth or inside the mouth. You need to get a hook solidly and deeply into the hard edge of the mouth for it to hold. Otherwise the hook pulls out or opens up, since only the tip has penetrated the jaw. With more gap it is easier to hook into the softer interior of the mouth or wedge around the inside edge of the jaw. There is also more metal to hold. Sound like tarpon fishing?

Larger gap hooks of the same shank length are generally stronger than shorter gap hooks, since wire diameter is usually matched to the hook size. However, this is usually just a slight increase in diameter, not a big jump like in a heavy wire hook. The functional strength of shorter hooks is that there is less leverage on the hook, meaning it’s less likely to bend or pull out. That is a reason most saltwater flies are tied on standard or short-shank hooks.


In basic hook reference, we have a standard hook-shank length and a standard diameter wire size. Variations from standard are usually designated by an “X” denomination. A 1X fine wire is finer; a 1X heavy is heavier; a 1X short is shorter; a 1X long is longer than a standard-shank length; and a 2X long is longer than that. That being said, hook designations change by brand, model and size. This is complicated in many standard dry and nymph hooks, as their proportions change in smaller sizes. Hooks that have an ideal hook shank-to-gap ratio in a size 14, may have a 2X long proportion in an 18. How does this help you? It is a starting point to determine which hook is right for you. To find the right hooks you can use designations, but for the best results you’ll need to physically compare hook length, gap, and wire size. Do this at your fly shop, club, with friends, or look in your own boxes.

Wet fly hooks all size 10
TMC 3761 – 1XL standard nymph hook
TMC 107SP – Short heavy nymph hook
TMC 2457 – Heavy scud hook
TMC 105 – Egg hook
Umpqua C300BL – Competition nymph hook.

Here are my recommendations. I’m going to use the TMC 100 standard dry-fly hook and a TMC 3761 1X-long nymph hook as standards. I’ve done some proportion measurements on hooks, comparing the gap to the shank, and this will give some insight into options for more gap. On both of these hooks the shank is about 2.3 times longer than the gap. If we want to get a bigger gap, we need a hook where the shank is shorter than 2.3. Pretty simple. My eyes knew this, and the measurements verified. For a dry fly a TMC 921 is about a 1.9 ratio and a TMC 3769 nymph is a 2.1 ratio. Similar models in a specific brand are the best way to start comparing. You don’t need a set of calipers to measure hooks—just set hooks out on a table to match them up.


For larger gap hooks these are models that I’ve found to be consistent in proportions as they change in size. For dry flies, stick with models that are designated as standard, fine or 1X fine, and make a judgement call on actual wire size. I want the strength. On wets, match the wire to the strength and weight desired. All things being equal, hooks with longer points tend to hold fish better.

Standard Dry: Daiichi 1310, TMC 9300, TMC 113BLH: 2.15 ratio

This is what I would call a standard-length dry-fly hook for smaller flies. I think they are a much better proportion than the TMC 100 hooks on flies below size 14. The TMC 113BLH is listed as a nymph hook in the US and as a nymph/dry in Japan.

Short Dry Fly: TMC 921, Fulling Mills Short Shank: 1.9 ratio

These are great hooks when you need gap and strength. These are “standard” wire. The Fulling Mills Short Shank was the hook I tied the winning Loop Wing Trico on, the one that won the One Fly.

Emerger/Dry: (Dai-Riki 125), TMC 2488, Ahrex AFW511, Umpqua 201: 1.5 ratio average

These are some of my favorite small dry fly and emerger hooks. For dry flies, simply ignore the slight bend in the hook shank. The 2488 is available in sizes down to size 26. These are good all-purpose small hooks for emergers, dries and nymphs.

Heavy Nymph Standard to 1X Short: Dai-Riki 075, Daiichi 1530, TMC3769, TMC 107SP: 2 ratio

These are great hooks when fishing for trophies and especially when using heavy tippet. Many steelhead nymphs are tied on these.

Scud Heavy: Daiichi 1120, Dai-Riki 135, TMC 2457, TMC2488H: 1.3 ratio

Curved-shank hooks are standard on scuds as well as many nymph patterns. People like the looks, but more importantly they hook and hold big fish. Curved imitations, like scuds and caddis larvae, are obvious patterns to use these hooks on, but most nymphs can be tied on these hooks. They are produced in a huge range of sizes from size six to 20.

Heavy Wire Egg Hook: TMC105, Dai-Riki 155, GAMAKATSU C14: 1.2 ratio

If you want a small hook for big fish this is it. What other size-10 hook can land large, anadromous fish? Short shank, big gap and heavy wire means big trout, salmon and steelhead in the net.

Competition Dry: Fulling Mills Grab Gape:. 1.9 ratio

Competition Nymph: Umpqua C300BL, C260BL, C550BL: 1.2—1.4 ratio

Competition-style hooks came from European nymphs fished in international competitions. They are similar to a scud or curved emerger hook, but they are barbless and have slightly longer curved-in points. The point helps hold fish on a barbless hook. Most of these hooks have a very large gap. This style of hook also crossed over into dry fly and nymph models. Czech companies, such as Hanak and Knapek, make the bulk of these hooks, but Japanese companies also produce them. The most common competition hooks in the US are sold through Umpqua and Fulling Mills. I have had good luck using the Fulling Mills Grab Gape hook on dries and emergers. Unfortunately, many of the competition hooks are found in limited sizes and in limited distribution.

Olive Scud, standard hook and large gap: Size 12 TMC 3761 1XL nymph hook and TMC Size 12 C550BL competition hook. The bigger gap helps in hooking and landing big fish.

Parachute PMDs: Standard dry fly TMC 100 size 16 and/or Fulling Mills Grab Gape size 12. Same shank-length, different gaps. Which holds big fish better? You know the answer.

Dry Fly Hooks, all size 14: TMC 100 traditional length; Daiichi 1310 (my standard length); TMC 921, short shank; Dai-Riki 125, emerger/dry hook; Fulling Mills Grab Gape, competition-style large gap.

Wet Fly Hooks, all size 10: TMC 3761 – 1XL standard nymph hook; TMC 107SP, short heavy nymph hook; TMC 2457, heavy scud hook; Dai-Riki 155, egg hook; Umpqua C300B, competition nymph hook.

Ten Going On 14 Nymph

This fly isn’t really a new fly, just a variation of the Pheasant Tail Nymph. However, it has a few twists on the standard. First, it is tied on a heavy wire shorter-shank hook for more gap and strength. You want to use a hook that has the same shank length as your standard fly, but a size or two bigger. Dubbing replaces the pheasant tail, so the fly holds up better when clamped in a large trout’s teeth. The fly is also tied to ride like a jig, but it isn’t tied on a jig hook. To make the fly flip over, a slotted bead is wedged down on the hook shank so that there is more mass on the top of the hook. And, after winding on soft hackle, that hackle is trimmed, which creates resistance. That combination of mass and resistance makes the fly flip over with the hook-point up. This fly works just about anywhere, but really shines on lakes.

Hook: TMC 107SP, sizes 10-14.

Weight: Slotted tungsten copper bead to match hook.

Thread: 8/0 Rusty Brown.

Tail: Pheasant tail fibers.

Rib: Small copper wire.

Abdomen: Pheasant tail colored Antron dubbing.

Thorax: Peacock Ice Dub.

Hackle: Dark dun hen.

  1. Crimp the barb and slide the bead on the hook.
  2. Invert the hook. Align the bead so the slot is beneath the hook. This will put more of the bead under the fly.
  3. Start your thread and wrap behind the bead. Make sure the slot of the bead stays down. Wedge the bead in this position with your thread.
  4. Cement the thread wraps.
  5. Rotate the fly upright. Tie in a few strands of pheasant tail fibers to make a short tail.
  6. Secure a strand of copper wire for the rib.
  7. Dub the abdomen.
  8. Rib the abdomen with wire.
  9. Dub the thorax.
  10. Tie in a soft hackle by the tip and make a few wraps.
  11. Whip finish and cement.
  12. Trim the hackle off on the top of the hook, which is actually the bottom of the fly. This helps it ride inverted.

Scott Sanchez
Scott Sanchez is a longtime resident of Jackson, Wyoming, and has stomped around the Yellowstone region for most of his life. When he’s not chasing elk during fall he’s tempting trout on an array of his unique flies, especially during the spring and summer season.