I use this product for only a few days, but for me it is absolutely perfect! Explanation:
For assembly, unscrew the screws and remove the belt clip to it and then just screw the new screws with the new attachment.
For the strap, remove the nut and the flat little thing, and put the strap on the screw, then turn the thing flat and tighten the nut.
Now he just have to engage the two parts!