ClipArt ETC
A wrench or spanner having a movable jaw.

Monkey-wrench

A wrench or spanner having a movable jaw.

"In order to get the best results from the tool the pressure on the handle should always be in the direction of the arrow shown above the latter, so as to put the pressure on the jaws at the points B and C, and not at D and E." —Grimshaw, 1902

Adjustable Wrench

"In order to get the best results from the tool the pressure on the handle should always be in the direction…