A piton is a metal spike (usually steel) that is driven into a crack or seam in the rock with a hammer.  The item otherwise has no direct description.

A set of ten pitons has a market price of 5 sp, and a weight of 5 pounds. A climber's kit also contains ten pitons.

These pitons are implied to be consumed if used to gain the +2 bonus on Athletics checks to climb.  The amount is not explicitly mentioned in the rulebook, although Pathfinder mentions that one piton is required for every 5 feet of climbing.[] Pathfinder also mentions that it requires 1 minute for each piton, although 4e may allow doing so as a standard action for each piton.