To easily attach a fastener to a simplified case at low cost and to attach it corresponding to the thickness of body to be attached at a prescribed attachment position.

In order to lock a lid element while closing it concerning the simplified case having the main body of case and the lid element for freely opening/closing the opening of the main body of case, a fastener 4 to be attached while facing through the prescribed attachment positions of the main body of case and the lid element is formed while being divided into a front member 41 arranged on the front side of that prescribed attachment position and a rear member 42 arranged on the rear side of prescribed attachment position so as to face the front member 41. Then, the front member 41 is provided with an engage pawl element 43 to be inserted and protruded in an attachment hole 2a provided at the prescribed attachment position, and the rear member 42 is provided with an engage hole 45 for inserting and engaging the engage pawl element 43. Besides, the rear member 42 is formed so as to have a push stop projection 46 protruded in counter direction and to be freely curved in the counter direction corresponding to thickness at the prescribed attachment position.