These are Multiboard Snaps that are attached to other Snaps. This allows you to snap two tiles together. There are three working variations: standard-to-standard (two standard snaps back-to-back), directional-to-directional (two moderate weight bearing snaps back-to-back), and face-to-hook (a folding hook snap that's two tiles thick).

I've also included a DS-to-hook version that has a few problems. The DS side sits a little proud of the tile that its attached to, and the B part can't be removed with the official part-B removal tool. I have to use a flat-head screw driver to remove the B part. If these problems don't matter to you, it otherwise works fine.