RJ (registered jack) patch panels are used to organise multiple network connections into a limited space. In this way, they work on the same principal as other types of patch panel, but are specifically designed to work with RJ connectors, which are a standardised type of connections most often used in telecommunications.
RJ patch panels consist of a number of different ports to which cables can be connected. The different ports are usually labelled to make organisation clearer, and this also makes it easy for individual connections to be added or removed from the network patch.
RJ patch panels can differ in the number of ports they hold, which affects how many different connections they can work with. This also impacts on the size of the patch panel. They may also be specifically designed to work with certain types of RJ connections, for example RJ21 or RJ45.