There's a bolt that runs from the butt to the reciever side plates, there's a flate plate the other end.
Another area that could cause a stress/crack failure.
http://support.crosman.com/hc/en-us/...C2200W-EVP.pdf
Scroll down to page 3 (I think it is), don't worry it's not the Sun.
Large flat bladed screw driver should tighten it.