X-ray vision tool !! - Instant boats are often created by flexing the sides around frames first, then laying sheets of plywood over top of the frames and sides and then glueing / nailing / screwing into place. You can make a very simple tool that will greatly aid you in the ability to drive a fastner thru the plywood and set into the chine log. Take 3 pieces of scrap wood sticks, clamp them so that they apear like a tuning fork. Then orient this so that one leg of the fork is under the plywood sheet touching the side of the boat, and the other is above the sheet where you will be driving your fastner. Draw this along the side and mark along the way, your pencil mark will show the outside edge of the boat which is underneath the plywood.