The four cantilevers on the control panel mod-ule shown in Fig. 1 hold the module firmly in place in the grid with their hooks, and yet it can still be removed when required. An economical and reliable snap joint can also be achieved by rigid lugs on one side in combination with snap-fitting hooks on the other (Fig. 2). This design is particularly effective for joining two similar halves of a housing which need to be easily separated. The positive snap joint illus-trated in Fig. 3 can transmit considerable forces. The cover can still be removed easily from the chassis, however, since the snap-fit-ting arms can be re-leased by pressing on the two tongues in the direction of the arrow.