Link 1 slides along leg a of the dividers. Leg a turns about axis A. Slider 3, moving along leg b of the dividers, is connected by turning pair B to link 1. When link 1 is moved along leg a, link 3 moves along leg b thereby spreading or contracting the legs of the dividers. The position of slider 1 is fixed by clamping with screw 2.
$991$LG,4L$