See question above. If one is staying in a hotel or a guest room, where it may be impossible to completely darken the room or it is Shabbat and the light was left on, and a separating Mechitza or curtain can not be placed, what can one do?

At night, when there is light in the room, in principle many Poskim forbid to have sexual relations even under the covers (Ra’avad; Smak; Ritva; S. A. 240:11 and EH 25:5; Eliya Rabba; MB 240:39). However some are lenient (Ḥida, Pesacḥ Einayim on Nidda 17b; Kaf Ha-ḥayim 240:71). Mishna Berura (240; 45) mentions that in a case of need, an ethical individual may indeed be lenient and rely on the darkness provided by a blanket used a cover.