If you've never fished a Pat's Rubber Legs for trout and salmon then I'd say you're missing a great tool for your toolbox. This fly can imitate a number of bugs, but most notably it imitates a tasty looking stonefly nymph. You can fish this pattern almost year round with success. I almost always start with this fly as my lead fly on a traditional suspension nymph rig. A little secret is tying them in two different sizes and fishing them in tandem.
It's not a bad tie. I taught this pattern in my final class for beginning fly tiers at Eldredge Brothers Fly Shop, and the students did a great job! Start with a size 8 nymph hook that has a 3XL hook shank. Wrap .025 non-lead wire from a hook eye length away from the hook eye back to the hook point. Secure the non-lead wire with black thread and tie in your rubber leg antennae and tail. Tie in the chenille near the bend of the hook and advance your thread forward to the hook point, tie in a set of rubber legs (about 2 inches long) then advance to the front of the non-lead wire and do this again. Wrap your chenille to the head of the fly, build a small head and whip finish. I like to apply head cement just to secure it some more.
Hook: Size 8 3XL nymph hook
Wire: .025 non-lead wire
Body: Medium black/coffee variegated chenille
Legs: Brown perfect round rubber legs