If you’re playing Rocksmith (and I think you should be), and you’re playing standing up (ditto), you have probably run into the "where do I put the controller" problem. The gamepad is required to navigate the menu system between songs, and if you play in a standing position you have to keep a stool or a table nearby to keep it within easy reach.
This simple mod mounts a spring steel clip to the underside of a standard Xbox 360 controller so you can attach it to your guitar strap. In this position, it is easily accessed with your strumming hand.
The steel clip I’m using is a common replacement visor clip for several models of garage door remote. A belt clip fitting, such as Tandy Leather’s 1238-00, should work just as well. The clip is secured to the Xbox battery holder in two ways: first with a short bolt that engages a small hex nut and lockwasher inside the battery holder, and second with a strip of double-sided foam tape that keeps it from rotating about the single bolt.
This mod does not affect normal controller operation in any way. The battery holder can still be removed and the batteries changed normally. In this position, the steel clip is inconspicuous and does not interfere with a normal gameplay grip, nor, significantly, with the controller’s resting attitude on a flat surface.