This type of “twin” rail is built from two separate pieces.

When bolted on a base: for example 50×50 M12 grid pattern plate, these form a rail which is 25 mm in height. So the installation of the base differs from Multi-Rail RM installation.

In this base rail the installation bolts are included.

Please note: Multi-Rail RM stoppers, clamps and riser blocks are compatible with the RL base rail and following instructions are applicable :
How to use Multi Rail RM