The wedge-lock is the orange piece that ensures the contacts remain fixed in the DTM body.  One wedge-lock is required per DTM connector body.  The number denotes the quantity of contacts, 'S' denotes socket contacts and 'P' denotes pin contacts. 

For example: A DTM06-08S connector uses socket contacts and has 8 of them, therefore you would use a WM-8S wedge-lock.