Boot bands are common outdoor gear, also used by US military personnel. 

They can secure or bind the legs, with the following functions:

• Prevent leeches and other creatures from getting under clothing on the legs.

• Serve as a clothesline during outdoor camping.

• Be used as an improvised tourniquet for emergency bleeding control to save lives.

• Suitable for many scenarios (compact and easy to use).

In addition, leg tie cords can be used for camouflage, helping vegetation attach firmly to helmets.