Abstract: Drywall Ripper is a sliding housing with a cutting mechanism for use with a T-square or the like. The preferred embodiment of the invention utilizes a housing, a slot in the housing with a magnet to hold a blade, clamping components within the housing activated with a clamping button on the housing, a release button on the housing to disengage the clamping components, a viewer opening on the housing, and a groove in the housing for insertion onto a T-square. To use the preferred embodiment of Drywall Ripper, an individual uses the groove to place the housing onto a T-square. The clamping button is then pressed to lock the clamping components of the device at the desired measurement on the T-square. The top of the T-square is then placed on a flat surface parallel to the ground and a piece of drywall is placed perpendicular to the flat surface, supported against its backside.