A whiffletree (also known as a whippletree) is a mechanism to distribute force evenly through linkages. The mechanism may also be referred to as an equalizer, leader bar or double tree. It consists of a bar pivoted at or near the centre, with force applied from one direction to the pivot, and from the other direction to the tips. Several whiffletrees may be used in series to distribute the force further, such as to simulate pressure over an area as when applying loading to test plane wings. Whiffletrees may be used either in compression or tension.