A portable frame assembly having a skid assembly for supporting a vertically oriented mast assembly is disclosed. The mast assembly is comprised of at least two column assemblies that may be extended or retracted vertically as desired. The mast assembly is translatable horizontally on the skid assembly without the need for tracks or rollers. The skid assembly may be positioned adjacent a wellhead for the purpose of performing plug and abandon operations. The skid assembly may include a power swivel and other such hydraulic or mechanical tools for performing a variety of operations on a well including removing and plugging well casing strings, milling pipe strings, cement drilling, removing wellhead assemblies, or setting and pulling plugs from pipe strings.