www.sparrowsusa.com

A Travelers hook sometimes also called a Shrum Tool is used to bypass Spring Latched and Dead latched locks. This is almost always used on doors that will open towards you where you can access the door jam. The long version is for reaching past plate covers that are trying to block this type of attack.

It can also be used to disassemble locks, rekeying, repining or repair.
Overall a pretty handy tool