Crain Tools 552 replacement blade, carbide tipped. 

The Super Saw features a powerful 13 AMP motor and a compact design that can operate in tight areas such as closets or pantries.  The saw can undercut doors in place, inside corners, and masonry...

This saw undercuts doors in place, inside corner areas, and can undercut masonry walls and hearths.  A diamond blade (No. 822) is available as an accessory for undercutting tile and stone. ...

This compact, 7 AMP undercut saw works best for fast undercutting of door jambs.  It can also undercut along walls, at inside corner areas, or beneath toe spaces.  Height of cut is...