Lenovo Z61t - Manual (Page 44)

9. With the notched end of the SO-DIMM toward the contact edge side of
the socket, firmly insert the SO-DIMM into the socket at an angle of
about 20 degrees 1 ; then pivot it downward until it snaps into place
2 .
10. Attach the palm rest cable connector to the system board firmly.
Replacing memory
36 ThinkPad ® Z61 Service and Troubleshooting Guide