This package includes four 1/2" x 24" Risers that are typically used with beginners to create varying degrees of incline in their layout. Risers are easily pliable to form curves and can be used on plywood or a foam base. To install, butt the sections firmly, pin into place with foam nails and connect. Foam Tack Glue is specially formulated for use with foam, but by using low temperature glue gun foam glue is the fastest way to assemble your foam backing.