@testforblock {type of block (not required)} {x,y,z} or {x,y,z} The Idea would be that this flag would test for a certain block at the stated coordinates (either the coordinates in the world or, if the coordinate had the ~ sign in front of it, the coordinate relative to the crafting table, brewing stand, furnace, etc. This means that the player might have to build a multi block machine to be able to craft the item. Then there could also be a custom failmsg for each block. So if the lava wasn't there: "You are missing your source of powaah!"