The "stitching" is from the temporary wires used to hold the edges of thin sheets of plywood together until they are "glued." The plywood is sheathed in fiberglass for strength. This is a quick way to make a rugged, lightweight small boat.
I was talking to John Harris at Chesapeake Light Craft last fall. As the conversation wandered around various boats and projects we were working on, it became apparent that we each had some issues that we might be able help each other with.
Because stitch-and-glue boat construction uses a relatively small number of wood pieces a boat can be build in relatively short order. Because plywood is inherently quite strong for its weight the resulting boat is quite tough and lightweight with a minimum of additional reinforcement.
Building a kayak using either the strip-built or stitch-and-glue method is within the means of most people who want to do it. Neither method is particularly difficult for anyone who is willing to take the time required.