The ProX XC-3MDF XLR Male to Female Feedthrough Adapter for Panel Mount from ProX is designed specifically for the kinds of wall panels often utilized in mobile gear and on stage. It features a zinc diecast chassis and a steel-element latch-locking device. This adapter offers a 3-pin XLR male on the panel side and a 3-pin XLR female on the back side.

These are handy for quick setup of a blank patch panel without soldiering connectors.  Simply plug a short cable into the back and attach to the output/input that you want to replicate on the panel.