Gemara

(Mishnah): Kohanim guard in three places in the Beis ha'Mikdash -- in Beis Avtinas, Beis ha'Nitzotz, and Beis ha'Moked.

Megilah 26b (Rava): I used to think that Kursiya (a chair or Bimah) is not Tashmish of Kedushah, for the Sefer Torah rests on a cloth on the Bimah. I saw that people the Torah is (directly) on the Kursiya, so it is Tashmishei Kedushah.

Rishonim

Rosh (Tamid 25b DH bi'Shloshah): The guarding in the Mikdash is not due to concern for theft. There is no poverty in the place of wealth. Rather, the Torah decreed to guard. Also, it honors the Mikdash not to divert attention from it during the day or at night.

Tur (YD 282): The chair prepared to rest the Sefer Torah on it is Tashmish Kedushah.

Beis Yosef (DH Tik): The chair is Kursiya mentioned in the Gemara. In some places they prepared a chair to put the Sefer Torah on it on a day when we read from two Sifrei Torah.

Poskim

Shulchan Aruch (YD 282:1): One must show great honor for a Sefer Torah. It is a Mitzvah to designate a place for it and honor that place exceedingly. One may not turn his back to it, unless it is 10 Tefachim above him. Rather, he sits in front of it seriously with fear, for it is the trustworthy witness on all people - "v'Hayah Sham Becha l'Ed." He honors it according to his ability.

Bi'ur Halachah (693:4 DH Motzi'in): Tosfos (Megilah 4a DH Pasak) says that on Purim we do not return the Sefer Torah it to its place (right after reading from it). Rather, one sits and holds it until they read the Megilah. The Levush and Derech ha'Chayim connote that we return it before Kri'as ha'Megilah. Beis Meir says that the Poskim did not bring Tosfos because also the one who holds the Sefer Torah must intend to be Yotzei hearing Kri'as ha'Megilah, and if he holds that a Sefer Torah his heart is on the Sefer Torah, like we say about Tefilah (OC 96:1 - one may not pray while holding a Sefer for this reason.)

Question: If in a Beis ha'Keneses there is no one wants to hold the first Sefer Torah during the reading from a second Sefer Torah, may they make a chair with holes (for the poles on which the Sefer Torah is rolled) to hold the first Sefer?

Answer (Igros Moshe OC 1:38): This is forbidden. The Shulchan Aruch obligates showing great honor for a Sefer Torah. This is why it is a Mitzvah to designate a place for it. One must honor it even for the short time that it is out of the Aron. Part of honor is that it is in a guarded, honorable place. Even if it is in an honorable stand in front of the Bimah, and not in back of the Bimah, which is in back of people, it is not guarded, since it is in a low, exposed place. Anyone can touch it! Even if no one will touch it, e.g. there are no children, it is dishonorable because it is not guarded. We find that there is honor in guarding, that they not take their minds off it. This is the grandeur and honor that the Bartenura and Rambam discuss. Even if someone supervises from afar, if it is not recognized, this is not honor. However, perhaps it helps to have an adult guard it while it is on the bench.

Igros Moshe: The Beis Yosef and Prishah explain that Korsiya was a a chair to rest the Sefer Torah on, on days when we take out two Sifrei Torah. This shows that there were places where they did not hold the Torah. Rashi and all the Meforshim connote that it was a table on which they read the Torah. Sha'ar ha'Tziyon (154:8) says that even though they do not put a Sefer Torah on it without a cloth, sometimes the cloth slips away and the Sefer is directly on the table (like Rava said). This does not apply to a chair on which we rest the Torah until we read from it. We do not open the Sefer Torah on the chair. It is wrapped in cloths! Even if the cloths are Batel to the Sefer Torah, and it is as if the Torah rests on the chair, there is concern for a cloth (on the Kursiya) slipping only if we must move the poles constantly (while reading the Torah). The Beis Yosef is difficult. We should not rely on him and the Prishah, for they did not bring this law in its place in Orach Chayim, and the Magen Avraham argues with them, and especially here where the custom was always that people hold the Sefer Torah. If they cannot find anyone to hold it, they should do like R. Yosi said in the Yerushalmi - they do not take the second Sefer out of the Aron until returning the first.

The questioner in Da'as Sofer (OC 20): We should forbid using a chair for several reasons. 1) The bench is not 10 Tefachim tall, therefore people must stand (YD 242:18). 2) One may not sit on a bench on which a Sefer Torah rests. 3) It is honorable to hold the Sefer Torah.

Da'as Sofer: Really, it suffices if the bench is a Tefach tall, like the Yerushalmi says. (Shach (282). The Beis Yosef says that this is in pressed circumstances; l'Chatchilah, it should be 10 Tefachim. The Beis Yosef brings from the Rashba that one Tefach does not help on a bed, but it helps on a bench that does not rock. Surely it is forbidden on a bed that goes up or down when people sit on it. The custom is in our lands is to have two such chairs, for it is hard to listen attentively to Kri'as ha'Torah while holding the Sefer Torah. Even though the Magen Avraham (144:6) permits rolling a Sefer Torah while they read from the first, the Acharonim wrote that the custom is to roll it during Pesukei d'Zimra. Even though we can distinguish between one who rolls and needs to see to roll to the place where they will read that day, experience shows that it is hard to have intent while holding a Sefer Torah. The Taz (96:1) asked why the Shali'ach Tzibur holds the Sefer Torah during Yekum Purkan, for this inhibits Kavanah. Such a chair was used in our Beis Midrash, in which the Kesav Sofer and Shevet Sofer learned. When the latter received Hagbah, he gave it to another so he could concentrate on the Haftorah; the other person put it in the chair.

Be'er Moshe (3:24): In Europe, the custom was to make a chair with holes to hold the second (and third) Sefer Torah on days when we read from two or three Seforim, or between Glilah and returning it to the Aron. Since the Sefer is in a separate Reshus, people need not stand. It was in a way without concern lest it fall. Perhaps the chair was made so people will not worry lest it fall. The Tur says that the chair is Tashmish Kedushah. The Beis Yosef says that this is Kursiya of the Gemara. In some places they prepare such a chair for when we take out two Sifrei Torah.

Be'er Moshe: I say that the reason it was put in a chair, and they did not give to a person to hold, is because they used to give it to youths to hold, for it is hard to hold it from Gelilah until returning it to the Aron, especially on days when they take out two or three Sifrei Torah, and a Ba'al ha'Bayis must hold it during all of Kri'as ha'Torah. Sometimes the Sefer Torah would almost come to disgrace (that no one wanted to hold it). Sha'ar(ei) Efrayim (10:6, and Hagahos Pischei She'arim 10) was unhappy about giving it to youths. They made a chair, so they would not need to give it to youths, lest a Michshol result. Perhaps Ba'alei ha'Bayis did not want to hold it due to the Taz. He said that a Shali'ach Tzibur may hold the Sefer Torah during Yekum Purkan, for then he prays for those who learn. This is like holding a Lulav in the proper time (which is permitted). Machatzis ha'Shekel permits also at the time of Birkas ha'Chodesh. According to letter of the law one must listen meticulously to Kri'as ha'Torah (146:2, Mishnah Berurah 15). When one holds a Sefer Torah, his mind is not free, for he fears lest it fall. This is why people refrained from holding it. Therefore, if people do not want to hold it, it is better that they have a chair than to give it to youths. The Bi'ur Halachah brings similarly from Beis Meir. Also, on Shavu'os our custom is to pray early, and almost all congregations in Europe did. Then there is great concern lest the one holding it fall asleep, for he was awake the entire night. Therefore, it is good to have a chair with holes and put the Sefer Torah in it. If initially the custom was to hold it, they should continue, if they can find adults to hold it. If one asks what to do, I answer that there should be a chair with holes and someone will sit nearby to guard it, but not on the same bench as the Sefer Torah (YD 242:18).

The questioner in Minchas Yitzchak (2:117): Surely they may not leave a Sefer Torah on a bench without anyone guarding it. Firstly, this can lead to disgrace of the Sefer. Secondly, people sit in line with the Sefer Torah, for the bench is not 10 Tefachim tall. Even if there is a bench exclusively for the Sefer Torah, and on the Bimah which is its own Reshus, and iron chains surround it so it will not fall, this is improper. The Poskim say that one holds the Sefer, due to its honor. Even according to the Beis Yosef who explains that the Tur discusses using such a chair, it should not be erect on the chair, rather, lying down. See YD 289:6. (The Mechaber rules like Rashi, that a Mezuzah should be vertical. The Rema is concerned for R. Tam's opinion, that it should be horizontal, so we place it on a slant.) The custom of Yisrael is Torah. Also in the Aron it is on a slant. Also on the chair it should be on a slant and fastened tightly. The chair should be special for this. The chair should be in a corner, so when one reads in the Torah, his backside will not face the Sefer Torah.

Minchas Yitzchak: I agree that one should not change from the custom. Sha'arei Efrayim says that the Sefer should be given to an adult. All the more so it should not be left alone on a chair! However, the Tur and Beis Yosef say that in some places they use a chair. The Chida said that this is proper. I say that it is proper that the Torah be on a slant even when a person holds it.