Hi Katsukiyo,

The problem with the "older" (CP-LCKNGWALLMOUNT) Wall Mount kit is that it uses the Pin holes from the articulating style "footstand" to mount the phone, which is not avalable on the IP Phone models like the 7931,7911,7912 and 7905 (see step b & c below)

b. On the back of the phone's footstand, push out the pins and remove the stand. You might need to use a screwdriver or other pointed device to push out the pins. The pins are firmly set, so it requires significant force to push them out.

c. Attach the bracket by inserting the pins in the same holes vacated by the footstand. The phone's ports should be accessible through the holes in the bracket

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/all_models/wallmount/english/install/guide/ippmount.html

So you must use;

CP-LCKNGWALLMNT2=

Universal locking wall-mounting kit

http://www.cisco.com/en/US/prod/collateral/voicesw/ps6788/phones/ps379/ps7062/product_data_sheet0900aecd80534259.html

7905,7911,7912

CP-LCKNGWALLMNT2=

From this guide;

http://www.cisco.com/en/US/products/hw/phones/ps379/products_data_sheet0900aecd8039de52.html

Hope this helps!

Rob