 For other designs, a floating brake mount has been used on some downhill oriented bikes, by means of a pole that connects the rear brake mount to the frame, as a sort of four-bar system for the brake alone.This type of system has mostly gone out of use due to the extra weight it brings, as brake jack is not considered as an especially significant problem.There are two types of linkage driven single pivots, those in which the extra linkages that connect the main swingarm to the shock play a structural role in the rigidity of the rear section, which are the four bar single pivot designs, and those in which this rigidity is assured by the swingarm alone.