fwiw on my canoe, i also decided to use a u-shaped bicycle lock for security. i made holes in both bow and stern for a piece of 3/4 inch (inside diameter) white pvc pipe. i put masking tape on each side of the canoe where i wanted the hole. i cut the end of the pvc pipe at the approximate angle so that when the cut end of the pipe was placed against the masking tape (you have to have the correct twist relative to the cut) it was flush and protruded perpendicularly to the centerline of the canoe. then i drew around the pipe leaving a circular mark on the masking tape. then (with a small (1/8 inch?) bit ) i drilled a series of holes just inside the scribed circle. i did this on each side (and at each end). then i was able to insert a small (coping) saw blade and cut through the bridges between the holes. this left a scallopped hole almost the side of the pipe. a little filing, then sanding with the sandpaper wrapped around the pipe (pushed through both sides at the same time) left an appropriate sized hold. the pvc was then epoxied in place, and sanded flat. this was all BEFORE my "end pours". the end pours were then made which really locked the pipe in place. on the outside you see a pleasant white rim of pvc (ala feathercraft). it fits the "kryptonite"-type bicycle lock. john tmc