That is part of a clip that holds the wires going to the x axis motor. if you pull off the frame on the right side you can see the wires that run to the motor. I believe the clip may be on one of the other motors as well but my memory is unsure.

check out the second image from this thing ----> http://www.thingiverse.com/thing:99811
Its an upgrade for the xyz wire clip, because at about 300 print hours that wire will fail from being bent too many times.