Now you need to fit and cut the thwarts to their finished length. They should fall a bit short of the gunwale on either end; the canvas should not touch them when it is on the boat. In the photo below, you are looking at the outside of the boat. That end should be cut at a compound angle: parallel to the outer gunwale. You can see the pencil line in the picture - the one one top is easy, just trace the gunwale. The vertical line on the thwart runs along a line from the guwale to the first stringer. This means it will slant in a bit at its bottom edge. The drawing below may show this better (angled face 2). After you draw the lines, you want to cut a bit (1/8") inside of the lines, so the canvas of the boat will not touch the end of the wood.
You can also see, in the drawing, the upper angled surface. This is created so that the thwart will fit more solidly to the undrside of the gunwale, which is slightly flared outward. This is about an inch long and takes off about 1/8" at the end. It can be done with a sander,or a sharp plane.
You need to drill a hole through each filler piece, where the thwart will be bolted to the gunwale. Drill parallel to the gunwale side (imagine poking the drill through that space if the filler wasn't there).
The finished attachment looks like this (below). The clamps marks, by the way, will be covered by the canvas and rubrails.
