A fastener structure (10) for connecting a first connector member (12) to a second connector member (14) having a slot (16) for receiving the first connector member (12). The first connector member (12) has a pair of generally parallel stiff yieldable legs (20) that are spaced apart a distance substantially equivalent to a width of the slot. The slot (16) has an open end (22) defined by confronting spaced apart sidewalls (24 and 26). The legs (20) have outwardly forming cam surfaces for camming engagement with the sidewalls (24 and 26), thus causing the yieldable legs to yield towards one another as the first connector member is pushed into the slot in the second connector member. The yieldable legs (20) have oppositely facing locking abutments (32 and 34) and the slot sidewalls have notched areas (36 and 38) for receiving the locking abutments. The fastener structure further includes a lock key member (18) that is slidable longitudinally between the legs and is engageable with confronting inner faces of the legs.