Is it permissible to “assemble” an elastic Shabbos belt on Shabbos (to put the keys on it in a way that will permit one to go out with it without transgressing the prohibition of carrying)? Is it considered makeh b’patish, since one is making the belt usable (if the keys are not put on correctly, one cannot use the belt)? Please give me sources. Thank you.
If the key is designed to be put on and take off for each usage of the key there would be no problem doing such assembly on Shabbos. If however it is meant to be put together and then used as such with the key attached, the belt should be assembled before Shabbos.