Foot Pads are dense foam pads or vinyl disks that attach to different Mounting Plates and Feet in the StructureLite product line. You can see them on page 143 of the StructureLIte Catalog.
Clear Vinyl foot pads are usually used when StructureLite Mounting Plates are used on assemblies that support glass like tables. Grey Foam foot pads are generally used when Mounting Plates and Feet come in contact with floors.
You'll no doubt find your own uses for Foot Pads when you 'Bring Your Designs to Life'™ with Gyford StandOff Systems™ machined aircraft-grade aluminum hardware product lines.