A bottom part of an enclosure for electrical installations, which comprises a rectangular bottom as well as a first wall and, opposite to the first wall, a second wall which are leading upward from the bottom, a third wall and a fourth wall opposite to the third wall, whereby the first wall of the bottom part has a first locking member (30a1) to fasten a cover to the bottom part, whereby the second wall has a first locking member (40a1) to fasten the cover to the bottom part, characterised in that - the first locking member (30a1) of the first wall comprises a first form-locking piece (7a, 7b, or 7c) which is detachably adapted in a first recess (3a1) formed in an outer surface of the first wall of the bottom part whereby the first form-locking piece (7a, 7b, or 7c) adapted in the first recess (3a1) comprises a planar outer surface (72a, 72b, or 72c) which is in the same plane as the outer surface of the first wall, and a first detent (39a1) formed in the first wall, adapted to prevent the removal of the first form-locking piece (7a, 7b, 7c) adapted in the first recess (3a1) from the bottom part to a direction away from the plane defined by the bottom of the bottom part, a stopper member (71a, 71b, or 71c) of the first form-locking piece (7a, 7b, or 7c) being adapted for cooperation with the first detent (39a1), - the first locking member (40a1) of the second wall comprises a second form-locking piece (7a, 7b, or 7c) which is detachably adapted in a first recess (4a1) formed in an outer surface of the second wall whereby the second form-locking piece (7a, 7b, or 7c) adapted in the first recess (4a1) of the second wall comprises a planar outer surface (72a, 72b, or 72c) which is in the same plane as the outer surface of the second wall, and a first detent (49a1) formed in the second wall, adapted to prevent the removal of the second form-locking piece (7a, 7b, 7c) adapted in the first recess (4a1) of the second wall from the bottom part to a direction away from the plane defined by the bottom of the bottom part, a stopper member (71a, 71b, or 71c) of the second form-locking piece (7a, 7b, or 7c) being adapted for cooperation with the first detent (49a1) formed in the second wall, and - the first locking member (30a1) of the first wall is diametrically located opposite to the first locking member (40a1) of the second wall. - the first locking member (30a1) of the first wall comprises a first form-locking piece (7a, 7b, or 7c) which is detachably adapted in a first recess (3a1) formed in an outer surface of the first wall of the bottom part whereby the first form-locking piece (7a, 7b, or 7c) adapted in the first recess (3a1) comprises a planar outer surface (72a, 72b, or 72c) which is in the same plane as the outer surface of the first wall, and a first detent (39a1) formed in the first wall, adapted to prevent the removal of the first form-locking piece (7a, 7b, 7c) adapted in the first recess (3a1) from the bottom part to a direction away from the plane defined by the bottom of the bottom part, a stopper member (71a, 71b, or 71c) of the first form-locking piece (7a, 7b, or 7c) being adapted for cooperation with the first detent (39a1), - the first locking member (40a1) of the second wall comprises a second form-locking piece (7a, 7b, or 7c) which is detachably adapted in a first recess (4a1) formed in an outer surface of the second wall whereby the second form-locking piece (7a, 7b, or 7c) adapted in the first recess (4a1) of the second wall comprises a planar outer surface (72a, 72b, or 72c) which is in the same plane as the outer surface of the second wall, and a first detent (49a1) formed in the second wall, adapted to prevent the removal of the second form-locking piece (7a, 7b, 7c) adapted in the first recess (4a1) of the second wall from the bottom part to a direction away from the plane defined by the bottom of the bottom part, a stopper member (71a, 71b, or 71c) of the second form-locking piece (7a, 7b, or 7c) being adapted for cooperation with the first detent (49a1) formed in the second wall, and - the first locking member (30a1) of the first wall is diametrically located opposite to the first locking member (40a1) of the second wall.