Double-tension is a method of applying tension to drum heads.

Drum manufacturers use several methods to apply tension to drum heads; the preferred way is to tighten the heads with a hoop that is held tight to the drum shell with a number of individual threaded rods which connect to stanchion

Stanchion

A stanchion is an upright bar or post, often providing support for some other object.* An architectural term applied to the upright iron bars in windows that pass through the eyes of the saddle bars or horizontal irons to steady the leadlight. A stanchion is an upright bar or post, often...

s mounted with bolts onto the outside of the drum shell.

When there are individual stanchions for both the lower head and the upper "struck" head, or when there is one common center-mounted stanchion that accepts the threaded rods from both the upper and lower drum heads, that is said to be a double-tension drum.