A mounting arrangement for mounting a reel shaft of a building opening shading device with its motor side shaft end on a reel shaft box, comprising: an end face lateral wall of the reel shaft box, on which provision is made for a mounting pin, and further an adapter disk attachable to the motor side shaft end, such adapter disk being provided with a centrical recess for being slid onto the mounting pin, and further a circumferential surface with cylinder segment shaped and/or level sections of a cross section which is constant or tapered in the direction away from the lateral wall, and further comprising a securing bolt which is movable between an anti-rotation position where the said securing bolt fixes the adapter disk in a non-rotatable manner to the lateral wall, and a rotation release position where it allows a rotation of the adapter disk, characterized in that the adapter disk on its circumferential surface is provided with at least a first bolt contact surface (10a, 10b) for the securing bolt, with the end face lateral wall being provided with a second bolt contact surface or provision is made for an adjacent case profile of the reel shaft box comprising the second bolt contact surface, and whereby in a defined locking rotation position of the adapter disk the first bolt contact surface (10a, 10b) and the second bolt contact area extend parallel to each other at a distance limiting a bolt insertion space, and whereby the first bolt contact surface (10a, 10b) forms a secant shaped section of the outer circumferential surface of the adapter disk, and whereby the securing bolt in anti-rotation position is located in the bolt insertion space and in rotation release position is pulled out of the bolt insertion space. an end face lateral wall of the reel shaft box, on which provision is made for a mounting pin, and further an adapter disk attachable to the motor side shaft end, such adapter disk being provided with a centrical recess for being slid onto the mounting pin, and further a circumferential surface with cylinder segment shaped and/or level sections of a cross section which is constant or tapered in the direction away from the lateral wall, and further comprising a securing bolt which is movable between an anti-rotation position where the said securing bolt fixes the adapter disk in a non-rotatable manner to the lateral wall, and a rotation release position where it allows a rotation of the adapter disk, characterized in that the adapter disk on its circumferential surface is provided with at least a first bolt contact surface (10a, 10b) for the securing bolt, with the end face lateral wall being provided with a second bolt contact surface or provision is made for an adjacent case profile of the reel shaft box comprising the second bolt contact surface, and whereby in a defined locking rotation position of the adapter disk the first bolt contact surface (10a, 10b) and the second bolt contact area extend parallel to each other at a distance limiting a bolt insertion space, and whereby the first bolt contact surface (10a, 10b) forms a secant shaped section of the outer circumferential surface of the adapter disk, and whereby the securing bolt in anti-rotation position is located in the bolt insertion space and in rotation release position is pulled out of the bolt insertion space.