From the Archive | Originally published September 2025. By: MidCurrent Staff.
The number of times I’ve knelt into a boulder, stretching to peer over at the water below, is too many to count. The number of brookies I’ve spooked doing that is probably too many to count as well. This Q&A comes from last September, and will help you avoid the thing I keep doing: spooking fish before my fly ever makes it to them. If I could add one thing, it’d be this: if you’re going to lean on a rock, don’t take the knee pads out of your waders!
— Caroline
Question: I’ve read that trout will hold on the upstream side of a rock, but how can I get a good drift there?
—Jeff A., Colorado (via the Ask MidCurrent form)
Answer: Water piling into the face of a boulder has to go somewhere, and some of it pushes back upstream. That leaves a small pocket of slow, recirculating water right against the rock, usually called the pillow. A trout sitting there holds in easy water with the main current running past a few inches away, so it sees food before the flow splits around the rock.
You can spot it from a slight dome or bulge in front of the boulder, or a patch of smoother water just upstream of the seams peeling off either side. Moderate current is what you want. Heavy flows churn the cushion up or push it out of reach, and very low flows barely form one at all. Not every boulder holds a fish up front, but enough do that it’s worth a cast before you fish the rest of the run.
Trout in the pillow face upstream, straight into the water you’d like to cast across, so come at them from below and stay behind them. Broken pocket water helps here, since the glare and noise on the surface let you get closer than you could in a flat run. Use the rock itself as a screen if the wading allows it.
Cast up and across from downstream and off to one side, with a reach cast if you need one, and land the fly several feet above the boulder rather than right on its face. The fly needs room to settle into the cushion, and a nymph needs room to sink. Drop it too close and the current sweeps it around the sides before the fish sees it. If depth forces you to stand upstream and fish down and across instead, that works, but only with enough broken water to cover you.
Fish the front pocket first. Your first drift is your best one, and working the seams and the tailout ahead of it will usually put that fish down.
A dry-dropper covers this water well. High-floating patterns hold up in the chop, so a Stimulator, Humpy, Royal Wulff, Elk Hair Caddis, or a foam hopper will do, with a beadhead nymph two or three feet below on 4X or 5X. Let the dry drift until it nearly touches the rock, because that’s often when the nymph gets eaten. If you’re nymphing straight, weight matters more than pattern. Tungsten beads and a slim profile get down inside a short drift, a tuck cast buys you depth, and jig hooks hang up less on whatever has collected against the boulder.
For a streamer, cast well above and beyond, mend enough that the fly doesn’t swing through too fast, and hold it in front of the rock as long as you can. A pause or a twitch as it enters the pillow is worth trying. If the slow swing does nothing, strip it hard across the front. The deeper the cushion, the heavier the fly needs to be, and flows shift enough through the fall that it’s worth reading each rock rather than assuming.
This version has been condensed; the original answer goes into casting angles, dry-fly patterns, and indicator setups.
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