The Mounting Offsets are used to offset the column away from the mounting wall to accomodate a foundation or other protursion that may exist at the base of the wall. If this is your case you will need a Mounting Offset for each mounting location that needs to be offset. The column without offsets is 1-3/8" from the mounting surface and the offsets add an additional 2-3/8" for a total offset of 3-3/4" from wall. Also, the lower mount bar is 18-1/2" from the floor. If you have a foundation or other protrusion at the base of the wall that exceeds 3-3/4" from the wall or 18-1/2" from the floor it is still possible to mount the lift but you may need to get creative.