The user will need to Equip, Turn On, and Calibrate the Device. 

Readings shall be taken by the on-board compass and the on-board gyroscope. These will tell the device its orientation on both the user and in reference to Earth's magnetic field. 

Using this information, the device will then compute which direction and intensity the knockers should vibrate according to the orientation information using an algorithm we shall develop.

Vibrations will happen at 45 bpm, to grant consistent information while also avoiding being bothersome.

The user will only need to Equip, Turn On (If Always-On Isn't Implemented), and Calibrate the Device. 

Instruction for equipping the device and calibrating it will be specified in the packaging on thick cardstock paper in braille!