7. Where to sit:[1]

It is customary to prepare a chair for Elijah Hanavi who is referred to as Malach Habris. The baby is placed on this chair when he is circumcised.[2] Some are accustomed for the Sandek to sit on this chair and hold the baby on his lap during the Bris[3], and so is the widespread Chabad custom.[4] Others however hold that the chair should be split into two parts and appear like two chairs.[5] For this reason some are accustomed to have a very wide chair for this purpose.[6] Others are accustomed to have two actual chairs, one for Eliyahu, and one for the Sandek[7], and so directed the Rebbe on one occasion.[8] Others have two chairs placed next to each other and cover them with a sheet so they appear like one chair.[9]

[1] Michaber 265:11; Siddur Admur; Tur 265; Rokeiach 113; Or Zarua Mila 107; Maharil Hilchos Mila; Pirkei Derebbe Eliezer 29; Mavor Yabok 4:5; Shevach Habris 15:1; See Pesakim Uteshuvos 265:27; See Encyclopedia Talmudit Vol. 4 Erech Bris Mila p. 249 footnotes 55

[2] The reason: The baby is placed on the chair in order to be blessed by Eliyahu the prophet. [Rokeiach ibid]

[3] Aruch Hashulchan 265:34; Sdei Chemed Mareches Beis Hakeneses 39

[4] Toras Shalom p. 79 that so was done by the Bris of the Rebbe Rashab, in which the Tzemach Tzedek was the Sandek and sat on the chair of Elyahu; Igros Kodesh 4:129, printed in Shulchan Menachem 5:110, that he is almost certain that so was done by a Bris in which the Rebbe Rayatz was Sandek; Reshimos of Rav Groner;  Shevach Habris ibid footnote 4; Koveitz Minhagim

[5] Derech Pikudecha Asei 2 Chelek Hamaaseh 13; Yad Haketana Mila 85

[6] Darkei Chaim Veshalom Munkatch 519

[7] Machzor Vitri 505; Orchos Chaim Hilchos Mila; Rokeiach 113; Maharil Hilchos Mila; Implication of Zohar 1:93

[8] Hiskashrus 644 that so directed the Rebbe to one individual

[9] Hiskashrus 645 p. 18 that so directed the Rebbe Rayatz; So was done by Rav Eliyahu Landa by the Bris of my son Eliezer Avraham in 5782