The Torah in Parashat Ki-Teitzei (22:8) introduces the mitzva of ma’akeh, which requires constructing a parapet around one’s flat roof for safety.
The Shibbolei Ha-leket, in discussing the laws of Chanukah (185), makes a surprising comment regarding a fence built around a roof. Just as Halakha forbids using Chanukah candles in a disrespectful way, the Shibbolei Ha-leket writes, it is likewise forbidden to use other mitzva objects in a denigrating manner, such as by walking on them. He gives the specific examples of tzitzit, a sukka, and a ma’akeh. According to the Shibbolei Ha-leket, it appears, one is not allowed to use the fence around his roof in any sort of belittling way, which could, conceivably, include, among other things, hanging laundry on the fence.
A number of 20th-century authorities, including Rav Yitzchak Weiss (Minchat Yitzchak 10:52) and Rav Shlomo Zalman Auerbach (Halichot Shelomo – Tefila, chapter 3), questioned this ruling. They argued that as the fence is erected solely for the practical purpose of protection, and does not serve any distinctly religious function, it has no halakhic status of sanctity, and there is no requirement whatsoever to treat it with any special degree of respect.
As for the particular question regarding hanging laundry on a ma’akeh, Rav Chaim Kanievsky (cited by Rav Asher Anschel Schwartz, Ma’adanei Asher, Ki-Teitzei, 5778) drew proof from the story told in Masekhet Sukka (10b) of Minyamin, Rav Ashi’s servant, who hung his wet shirt on Rav Ashi’s sukka for it to dry. Rav Ashi told Minyamin to remove the shirt from the sukka, as people might think that it was placed there as part of the sekhakh covering over the sukka. One of the qualifications of sekhakh is that it must be made from raw material, such that it is not susceptible to tum’a. Garments, of course, are able to be worn, and are thus susceptible to tum’a and hence not suitable as sekhakh. If people would see clothing on top of Rav Ashi’s sukka, he feared, they might deduce that clothing may be used as sekhakh, and they would then build sukkot which are unsuitable for the mitzva. It seems quite clear that otherwise, had it not been for this concern, Rav Ashi would not have objected to having clothes hang to dry on the top of the sukka. Rav Kanievsky thus proved from this story that hanging laundry on a mitzva object – such as a sukka or a ma’akeh – is permissible, and even the Shibbolei Ha-leket would allow it, since this is not degrading to the mitzva object.