A closure (10), for connecting two thin walls, such as sheet metal doors (12) to sheet metal frames (14), is disclosed, which comprises a mounting piece (18), arranged in or on an opening (16) in the first thin wall and a shaft (20), retained in the mounting piece and which may be rotated and axially displaced therein. A pivoting lever (24) is mounted on the one outer end (22) of the shaft (20), which may be pivoted about an axis (28) perpendicular to the axis (26) of the shaft and, on the other inner end (36) of the shaft, a retaining piece (38) is arranged, which may be engaged with an opening (66) in the second thin wall (14). According to the invention, the retaining piece comprises a cupular guide piece (42) and a sleeve piece (44), which may be inserted in and rotated in the cupular guide piece (42) against the force (40) of a spring. A catch (46) projects from said sleeve piece (44) in the direction of the wall plane (50), which, in the engaged position, extends beyond the outer surface of the guide piece (42) as far as the rear surface (50) of the second thin wall (14) and rests thereon.