I purchased this for my daughter. Unfortunately, it goes under the car seat. I have my car seat professionally installed and it certainly wouldn't be convenient to be taking it back to the police station once a month to have them unlatch my car seat and reposition the foot rest. Not only that, the cloth material isn't the non-slipping material that should go under a car seat to prevent slippage. Basically, this could be a real hazard and I doubt anyone who installs car seats would okay it. Needless to say, I found "Happy Feet" on Ebay that just hooks around the seat (I ordered that but haven't received it as of yet).

It doesn't really work well. Because it's velcro it tends to come apart under the seat when trying to adjust it...

This foot rest has been such a help for our little guy who wears braces and need a comfy place to rest his feet. We've had no problem with adjustments or installation.

I purchased this item for my child to use on a 7 hour road trip. Completely useless! I used an ice cooler as a foot rest.

This works great to keep my daughters legs from simply dangling over the edge of the car seat. Also gives her somewhere other than the back of the passenger seat to put her feet! Simple to use also, just slide under the seat and the childs weight keeps the mat in place. "adjustable" in so far as you decide how much goes under the seat. Worth $20.