Hi-Lift Jack HKR Red Polyurethane Handle Keeper For Hi Lift Jacks

You slide it on - it keeps the handle in place. works as intended.

To be honest, it probably should have come with the Hi-Lift jack (as many of the "extras" should have) but it works very well and is cut quite nicely to fit. It only (obviously) holds the jack handle at one angle though, so make sure that's not a problem however you mount yours.