I was a guest by someone on Shabbos. He and his Rebbetzin were having a hard time opening a bottle and asked me if I could open it. What is the correct and courteous response can I simply reply that my custom is not to open bottles during Shabbos?

On question 4087 regarding the proper way to open the common grape juice bottles of our days, since one may be turning the cap into a usable utensil, as after the ring that attaches it to the bottle is broken and separated from the cap, it can be reused many times and should be considered as having created a new ‘Keli” or utensil which is prohibited on Shabbos. We wrote that: Therefore, Horav Shlomo Miller’s Shlit’a opinion is that the best way to open the bottle of juice is by first making a hole with a pointed knife on the cap of the bottle, (carefully avoiding to destroy or obliterate any letters), thus destroying its value as a utensil. (see also Shmiras Shabbos K. 9: 61). After, having done that you may be stringent and have two people open the bottle with a ‘Shinui’ or a different way of doing it normally. One may just hold on to the cap firmly without turning it, while another would turn the bottle itself and thus detach it from the cap. However, Horav Shlomo Miller’s Shlit’a opinion is that this second step is unnecessary.