Double-leaver Mechanism or Rocker-Rocker Mechanism:

In this mechanism, both of the links 2 and 4 can just oscillate. This is illustrating in Figure.          

Link O₂A oscillates among positions O₂A₁ and O₂A₂ whereas O₄B oscillates among location O₄B₁ and O₄B₂. Location O₄B₂ is obtained while O₂A and AB are along straight line and position O₂A₁ is attained when AB and O₄B are along straight line. This mechanism ought to satisfy the following relations.

(l₃  + l₄ ) < (l₁  + l₂ ) (l₂  + l₃ ) < (l₁  + l₄ )

It can be observed that link AB has shorter length as compared to other links.

If links 2 & 4 are of equivalent lengths and l₁ > l₃, this mechanism produced automobile steering gear.