[JRTJH]

Slide Jacks (actually slide braces or blocks) were conceived waaaaay back when slides were called "tip-outs". They were hinged at the bottom and "tipped out" of the main trailer body sidewall. The blocks were installed under the tip-out to prevent it from extending too far and to help keep it from ripping the sidewall out of the "then often wooden framed trailer body".

Evolution changed those slide blocks to slide jacks which were adjustable so users didn't have to "use wood blocks or rocks/bricks to adjust their height to get the tip-out floor level.

Then along came "trailer slide-outs"... They eliminated the need for tip-out blocks, but the manufacturers "evolutionized" or "revolutionized" the "tip-out blocks" and marketed them as "slide jacks"... It's all a "money thing" more so than a "necessity thing"...

Modern slides don't require blocking/bracing/jacking to keep them stable and any such device can cause much more damage than it can provide stability...

Save your money for another barrel of "adult beverage".....