Beloved TC Electronic Noise Gate up for sale. There are no issues with this equipment but I no longer use it. There is loop-side velcro on the bottom but I can remove it without leaving any residue if you prefer it without. The bottom screw is accessible through the velcro in case you need to open it up.
The TC Electronic Sentry can be modified via the TonePrint app to do a wide range of gating options not available via the switches and knobs but that was a little too in the weeds for me so I never tried that out.