These are blocks that resemble the P-Switch from Super Mario Bros. 3. pswitch.asm and upsidedownpswitch.asm are the actual P-Switches, pswitchquestion.asm is a block that spawns one of these two blocks. You have to adjust the Map16 number in the .asm file. Various other things can be changed too.
Screenshots:
An updated version already exist in our section so this version is obsolete (GHB's version is reusable so it has got a different use from the SMB3 P-Switch).