Abstract: The instrument comprises two rigid yokes 1 and 2 capable of sliding one with respect to the other in the direction of the clearances to be measured between two components (R, 5) and 8. First of all, using an operating member 3, enough force to bring the ball R against the stop b1 of its socket is exerted on the component 5 by means of a spring 10. The comparator 9 is zeroed. Enough force is then exerted on the component 5 to bring the ball R to rest on the opposite stop b2 of its socket, this being done using an operating member 4 that acts in the opposite sense, the clevis mount 8 still being held between two resting faces 6, 7 of the yokes 1, 2. The clearance of the ball R in its socket is then read directly off the comparator 9. Application to measuring clearances in ball joints.