Bondo

From Wikipedia...

Bondo is a 2 part putty used to fix dents in cars, created by Bondo Corporation. While the term "Bondo" is a brand name for this company's product, it is commonly used as a genericized trademark to refer to all auto-repair putties or so-called plastic body fillers. Bondo is a two-part epoxy that when mixed turns into a putty which then sets and becomes rock-hard. The user can apply the mixed Bondo to the dented panel, sand it to the proper shape, and prime and paint it like the metal around it. It may also be used to Modify the look of PC cases, as some people do to make it look cool, using the bondo as a sort of clay to make items to paste on the case.

When building a home arcade cabinet, Bondo is commonly used to repair errant saw or router cuts, holes left when countersinking screws, and other applications. Wood filler or putty can be used as well, but sometimes wood filler expands over time, leaving a visible mark.