Umbrella with no marit ayin
I work for a Jewish old age home in a small Jewish community. Every other Shabbat I lead Shabbat morning services for the Jewish residents of the home. However in order to do this I have to walk over an hour to the old age home and an hour back (all within an eruv). If I don’t lead services than it is likely that the residents will not have any davening during Shabbat. Not infrequently there are rainstorms which make the walk very difficult (even with a rain jacket). Would it be mutar to use an umbrella opened before Shabbat that has printed on it’s fabric in big letters המטריה הזאת נפתחה לפני כניסת השבת? After all, what more obvious siman is there than this?
There are opinions that using an umbrella actually involves a prohibition of Ohel, even if opened before Shabbos, similar to the opinions that placing a hat on one’s head could be ohel. Others hold it is only a question of maaris ayin. While your suggestion is innovative, it does not deal with the first issue of Ohel, and even in regards to the second issue, putting a sign does not necessarily take away the issue of maaris ayin. People may see the umbrella and not the sign, or see the sign but assume it is permissible in any event, as is human nature, especially for those who are not learned.