A wall chaser is a power tool

Power tool

A power tool is a tool that is actuated by an additional power source and mechanism other than the solely manual labour used with hand tools. The most common types of power tools use electric motors. Internal combustion engines and compressed air are also commonly used...

 used for cutting narrow grooves in walls.

Wall chasers are usually powered by an electric motor

Electric motor

An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

, which in turn drives two abrasive discs like those found in an angle grinder

Angle grinder

An angle grinder, also known as a side or disc grinder, is a handheld power tool used for cutting, grinding and polishing.Angle grinders can be powered by an electric motor, petrol engine or compressed air. The motor drives a geared head at a right-angle on which is mounted an abrasive disc or a...

. The abrasive discs are placed closely together.

Uses

Wall chasers are quite a specialised tool and are generally only used for cutting a groove into a wall. An electrician for example would perhaps use a wall chaser when laying electrical cable. Once finished the groove can be then plastered back over to leave no sign of what is beneath.