What do ladder bars do ?

Ladder bars have the ability to adjust pinion angle "under the car" so what that is worth....I don't know how a leaf and a ladder can coexist unless they are the same length to the eye and mount and the lower bar is inline with the lower edge of the axle. Sure it can be calculated but fully adjustable coil overs would be lighter than SS springs by then. Not saying it didnt work for 33IMP but without the sliders that would be an engineered setup.