Wand of digging
|A magical device which drills tunnels through unworked rock.|
A wand of digging will remove rock walls in a straight line in the direction zapped. It affects only rock walls, whether normal, transparent or translucent. It will have no effect on non-rock walls; e.g., stone walls, metal walls, crystal walls, beeswax, statues, "unnaturally hard" walls, etc.
A wand of digging is quite useful for digging passages into otherwise inaccessible areas, to escape incoming enemies, or to create corridors so as to fight only one enemy at a time when faced with a group. Equally, it can be used to broaden existing corridors to increase access to a monster (say, by a summoner aiding his horde). Even as a formicid character you can benefit from it by saving some time, because it digs tunnels much faster than the digging ability.
Prior to 0.12, monsters would never use wands of digging.