Some people use for Hanukah a Menorah that has a "back," meaning, a wall behind the candles, which obstructs the view of people standing on the other side. The question arises as to how and whether such a Menorah may be used for the Misva. The purpose of lighting the Hanukah candles is to make them visible to the public, and this purpose is obviously not achieved if people looking at the window see only the back of the Menorah, and not the candles. On the other hand, if one turns the Menorah around so it faces the window, he will not realistically be able to light it. One might suggest lighting the Menorah and then turning it around to face the window, but Halacha forbids moving the Menorah after the candles are lit (Mishna Berura 675:6).
Hacham Bension Abba Shaul (Israel, 1923-1998) addresses this issue in his work Or Lesion (vol. 4, p. 280; listen to audio recording for precise citation), and he writes that if one uses such a Menorah, he should turn it on an angle so that he will be able to light it and it will be seen by people outside. By turning it around partially, one ensures that he will be able to light the candles while still allowing people outside to see the lights.
Summary: If one uses a Menorah with a back wall, he should position it on an angle such that he will be able to light it but it will also be visible to people outside.
