Here is your answer straight from wikipedia

The Classic Controller contains slots on its backside, opened via a rectangular button at the top of the controller, presumably for attaching the controller to something else.[55] The purpose for these slots remains undisclosed,[56] but it is commonly believed to be used with a special clip that attaches the Wii Remote to the Classic Controller, enabling it to take advantage of the Wii Remote's motion-sensing and rumble capabilities (the Classic Controller does not have its own accelerometer or vibration motor); Nyko has released such a clip, in addition to a grip shell and a place to store the cable.
Source(s):
http://en.wikipedia.org/wiki/Wii_Remote#Classic_Controller


Permalink | Report