The MCS-Joiner 3K from JL Cooper is a hardware kit, intended for physically connecting MCS 3K series modules. The kit consists of two plates, one for the bottom and one for the top of the units, and includes mounting hardware.
One kit is required for each additional module that is to be connected, and the procedure is user installable.
In the Box
JLCooper MCS-Joiner 3K - Hardware Kit for Connecting MCS3K Series Modules