I'd say at this point in my woodworking career I've folded 17,635 pieces of sandpaper for the purpose of hand-sanding. By hand-sanding I mean just that, nothing more than hand and sandpaper. Technically, of course, using a sanding block is hand-sanding, but so often more precision is required for such tasks as smoothing a joint, removing a blemish or scratch, especially smoothing curves or contours, etc. Nothing like fingers and a little piece of folded sandpaper does the trick. Doubling the sandpaper by folding it in half seems natural and provides better purchase. Years ago I thought wouldn't hand-sanding be easier if the two smooth sides were not always slipping and sliding about? This could be accomplished merely by gluing the fold together. As is often the case with our own best interests this fine approach to sanding was defiantly deferred. Until last week. I finally took the typical quarter sheet strip of sandpaper (2.75”x 9”) used on a standard sanding block, cut it in half, creased the pieces in two, sprayed the backsides with light duty adhesive and then folded the tacky surfaces together. Voilà! Using three sanding block strips I made a half dozen of these all at once.