Small edges that create puzzles and can be matched together. They look like matchboxes so here is the name. Be aware they are nasty! Use them only if you are strong enough. Otherwise do not bother and look elsewhere. These are small incut edges. You can call them crimps if you like. We have seen some strong guys succeeding in overhang. Could be used on slight overhang? Yes, but for beginners we would recommend setting on in slabs.