Recommended: Four slides for a rigid assembly. Mountable to any face.
Recommended: Three slides if only mounting to only one face (the middle slide face)
Caution: Two slides if a very stiff L bracket is used that mounts to both faces
Not Recommended: One slide, which can't control the slides location relative to the rail.
The slide inside face is spaced 1mm away from the rail when two or more slides are used, as is not meant to contact the rail.
Parallel Rails
Recommended: Four slides on rail 1, One slide on rail 2
Recommended: Three slides on rail 1, One slide on rail 2
Recommended: Two slides on rail 1, One slide on rail 2
Caution: Four, Three, or Two slides on rail 1, more than One slide on rail 2, which can cause binding if the rails are not exactly parallel
Not Recommended: One slides on rail 1, One slide on rail 2, which does not control the slide location relative to the rail