Trailer aid chock

Does anybody have the trailer aid chock that you drive up on that raises the other wheel to change it or work on it ? I was wondering how high and long it is. I want to fabricate something at work to use.
Thanks

I bought one and returned it. It didn't get my other tire off the ground and I thought it was narrow. I like to see all or at least most of the tire on the boards or whatever you use. I now run my good tire on a 2" board and use a bottle jack for the one I need to change. It takes some of the pressure off and the bottle jack doesn't work very hard. I used this method to remove my tires and have them balanced. It worked pretty good.

I use a wierd cut board that I just happen to have at the house, its about 2' long and about 3.5" tall by 6" wide,
I place a couple of my square 2x6 boards I use under the legs in front of it and one on top of it to make a make shift ramp to roll up on. I guess that makes it right at 6" tall when done, I'll have to measure it to see for sure, But when your on the side of the road and need to move quick it will raise the tire off the ground about 2".
If your tire seperates you'll need to roll the busted tire up on a board to loosen the lugs then roll it up on your bigger board. I had my flat changed in about 20min, Taking the bikes off the rack and getting the tools and boards out took longer than changing the tire itself.

I keep'em in the back of the truck ready to use. either for blocking up the legs or changing a tire.