This package includes four 2"x24" Risers that are used to elevate your track. Risers are easily flexed to form curves and can be used on plywood or a foam base. To install, butt the sections tightly, pin in place with Foam Nails (ST1432) and attach. The Low Temp Foam Glue Gun (ST1445, and Glue Sticks ST1446) is the fastest way to assemble your foam base, but you can also use Foam Tack Glue (ST1444).