Expansion joints must be filled with an elastic filler material, such as epoxy based Devcon Flexane 94, to maintain expansion properties. For temporary moves, sheet metal overlays (20 gage or thinner) can be used to bridge the gap, allowing Air Casters to move over the joint. The leading edge must be taped with high-quality, 3-inch tape. Sheet metal should be wider than caster size. For an 18- or 21-inch caster, we recommend a 24-inch material.