TheRevJosh

I use the screw jacks in addition to the x-chocks. They work to counteract different movement. The screw jacks do a good job of reducing the up and down, while the x-chocks cut down on the fore and aft movement. You got a great deal on the screw jacks, just put them right in front of and behind the axels and you'll be amazed the first time someone uses the stairs.

humblerb

I used them and thought there was a slight difference, but hard to tell.
I only bought two (all they had). I guess it makes sense to have four.
Going to try the x-chocks, too.