1. Make a cut using whatever small saw you have on hand--keyhole, reciprocating, oscillating--at each side of the opening just down to floor level.

2. Use a chisel or other sharp tool to split the grain at floor level, shaving off a thin strip.

Alternatively, install some plastic feet on the front of your wardrobe and forget about it.

1. Make a cut using whatever small saw you have on hand--keyhole, reciprocating, oscillating--at each side of the opening just down to floor level.

2. Use a chisel or other sharp tool to split the grain at floor level, shaving off a thin strip.

_________ ___________________ ____________ <-- top of protruding board 
_________|___________________|____________ <-- floor level
               ^-- chisel here
         ^-- vertical cuts --^
         

Alternatively, install some plastic feet on the front of your wardrobe and forget about it.