There’s an inherent problem with the way that standard receiver hitches and accessories are built. No hitch manufacturer wants to build a hitch that’s too small for the average accessory (ball mount, bike rack, etc)., and no accessory manufacturer wants to build an accessory that’s too big for the average hitch. As a result, both manufacturers err on the side of caution and the result is a huge amount of slop on most hitch/accessory combinations. The result of this is a ‘clunk’ or rattle when turning with a trailer and, even worse, a magnification of the backlash at the top of bike racks, causing excessive swaying/looseness.
There are a number of ‘solutions’ to this problem. One of these solutions requires the accessory side to have threaded hitch pins, this is a no-go for bike racks (where the problem is the worst) since there aren’t any made this way. The other solution is a device that wedges between the hitch and accessory. This only works on one axis and would require extra tools/setup every time the accessory is connected/disconnected.
The alternative to this, which I’ve seen other examples of online, is to drill/tap a hole through one edge of the receiver so that a bolt can be used to push two of the flat sides of the accessory against two of the flat sides of the inside of the hitch. To get plenty of threads I went a step further and welded a nut (with small section of tube to fill the gaps) to the receiver. This also significantly reinforces the edge of the hole to negate any compromise in strength created by drilling the hole. This isn’t much of a concern though since most of the forces are transmitted through the hitch pin which is well in front of the new hole. For tool-less deployment and removal I fabricated a bolt with integrated handle, much like what’s found on bench vices. I eventually painted this bolt also, but it’s not shown in the pictures; I’ll leave this in the trunk when not used. The hitch rattle/clunk is now completely gone, plus it’s easy to deploy and will work for every hitch accessory.