The MTP Drop Sling Strap for Osprey, allows you to attach to your body armour.
 
Fitting Instructions
The Drop sling is secured to the rear of the vest, using a T Bar fed into a rear Mollé.

Firstly detach the T Bar and D ring from the sling assembly
Feed T Bar and D ring through the MOLLE webbing
Reattach the sling ready for use.