A hand-forged iron spike the length of a man’s hand, tapered to a chisel point and finished with a looped eye at the head. A climber drives it into a crack, seam, or mortar joint with a climbing hammer, then clips a carabineer or threads a short sling through the eye to anchor rope or handhold. The steel bears the weight of a full-grown man under sudden strain; quality pieces ring when struck and seat cleanly, while a poorly-forged piton rings dull and may shear under load.
As a rule of thumb, a climber on serious vertical work places roughly one piton every ten feet of ascent — less on easy terrain with frequent natural holds, more on a blank face or overhang. Pitons are consumables in practice: driven deep, they are usually left in place when the climber descends, and a long ascent can cost a handful or more. Siege engineers assaulting a fortress, steeplejacks working a tower, and mountain scouts traversing a cliff all budget their pitons the way an archer budgets arrows — by the dozen, bought in bulk before the climb and rarely seen again.