Ice screw

[1][2] Ice screws may come with one or more of the following: an in-built or separate ratchet mechanism to speed up placement, conical centre-hole to aid removal of ice cores, different lengths, different numbers of cutting teeth, different cutting angles, different surface finishes, and different size clip holes.

Price and durability are usually design considerations too, as a usable rack of ice screws will be a significant financial investment for many climbers.

This surprising result is thought to be due to the previously underestimated role of the threads in holding the screw in place.

A piece of wire - typically a piece of old coat hanger shaped for the purpose - or a stiff flexible purpose built tool with a small hook at one end and a hanging loop at the other end, is often used to aid threading of the cord.

In the Rosetta project, the European Space Agency equipped its lander with multiple ice screws to obtain stability on comet surface, but they failed to hold, and the lander bounced a significant distance from the initial landing site.

An ice screw. Some modern screws like this one now have a handle to assist entry and removal, whereas early models did not.
Development of ice screws for the period 1924-2000
Two ice screws placed to form a solid climbing anchor point
Climber placing an ice screw