(4H) 4 Hole mount is typically used on flexible material that is not strong enough to support the movement from the center (CMT).
(CMT) Center Mount used for mounting to translucent or thin materials.
(FA) Front access used for mounting the clock movement into a solid wall where access is not available from the rear (RA).
(RA) Rear access used for mounting the clock movement into a solid wall from the rear.
Specific information on this style of movement is available at the link here.
Additional information available in the documentation tab above.