The Offset Mount Plate is used to offset the colomun 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 an Offset Mount Bkt. for each mounting location that needs to be offset. The plate offsets the column an additional 2-3/8" for a total offset of 3-3/4" from wall. The lower mount bkt is 18-3/4" 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 18-3/4 it is still possible to mount the lift but you may need to get creative.