Low Rack Leg Support
The low rack leg support is required for all single-riser MultyRack setups. The leg is designed to take some strain off of the low rack cross bar when it's loaded.
When the MR-105 riser is installed in the center of the high rack & low rack, it will cause the rear bar to flex in the center. This leg support is to prevent that from happening.
However, if one or two MR-105 bulwark risers are installed on the outsides of the high rack & low rack (and not the middle), the weight is distributed in a way that does not put nearly as much strain in the middle of the low rack cross-bar.