# One of the biggest limitations in the melacha of Boneh is its application to keilim, moveable vessels that are not attached to the ground. ''Ein binyan b’keilim'' is a concept that appears in several Gemaras<ref> Shabbos 102b, 122b and Beitzah 11b are some examples </ref> and is the subject of an enormous machlokes<ref> According to Rashi Shabbat 74b s.v. ve’iy there is no issue of boneh when constructing a utensil and only if it is attached to the ground is it boneh, altogether either way it’ll be macah b’patish. However, Tosfot s.v. chavita argues that creating a kli is also boneh as the gemara Shabbat 102b cites the opinion of Rav who holds that assembling a shovel is boneh. Maginei Shlomo Shabbat 102b answers Tosfot’s question based on the Ramban (Milchamot Shabbat 37a) who explains that many other amoraim disagree with Rav and hold that there's no boneh in constructing utensils. See Peni Yehoshua Shabbat 74b for another answer. Nonetheless, the conclusion of most rishonim is that it is boneh to create a utensil from scratch like Tosfot. This is the opinion of
Ran (on Rif Shabbat 37a s.v. makshu), Ramban (102b s.v. rav), and Rashba (102b s.v. hay). For further reading, the sefer Binyan Shabbos (Part 1) dedicates several chapters to this topic. </ref> among the rishonim, achronim, and poskim. Despite the all-encompassing implication of “ein binyan b’keilim,” most rishonim and poskim say that there are situations when one can make a kli and be chayav on a biblical level for Boneh. The general consensus among most rishonim is that Boneh does apply to keilim when one makes a kli in its entirety<ref> Chiddushei HaRamban, Shabbos 102b, s.v. Rav Amar. Also see Tosfos, Shabbos 74b, s.v. Chavisa </ref> or if one uses strength and craft (''chizuk v’umanus'') in the process of making it.<ref> Tosfos, Shabbos 102b, s.v. Hai. It should be noted that Rashi (Shabbos 47a, s.v. Chayav Chatas; Beitza 11b, s.v. d’ein) seems to be of the opinion that there is no concept of binyan b’keilim at all. However, Rashi says (Shabbos 47a) that there are cases, like making a kli in its entirety, when one would be chayav for makeh b’patish. </ref>
# Making a utensil loosely is permitted if it usually is made loosely, but it is forbidden to fit it together tightly or even loosely if it usually fits together tightly.<ref>The Gemara Shabbat 47a cites a dispute whether constructing a bed in a loose fashion is permitted but everyone agrees if it is tight it is forbidden. The Shulchan Aruch 313:6 rules that if it is loose it is permitted. Rama 313:6 writes that it is only permitted to assemble a utensil in a loose fashion if it is normally loose, however, if it is usually tight and you just made it loose once there is a concern you'll make it tight this time. The Bet Yosef cites this concept from the Hagahot Ashuri Shabbat 3:23 and infers it from the Rambam 22:26.</ref> For example, constructing an army cot from pieces that come apart on Shabbat or Yom Tov is forbidden since the legs fight in tightly.
## If a shtender is made of multiple pieces it is forbidden to construct or reassemble if it is apart unless it is so loose that the pieces would wobble in their sockets.<ref>Shulchan Aruch 313:6 cites a dispute whether constructing a cup is similar to constructing a bed. Mishna Brurah 313:45 explains the dispute is whether a cup which is which put together tightly but not hammered together is judged like a bed or not. Mishna Brurah 313:46 writes that initially we are strict to assume that it is the same halacha as a bed but if there's a need of Shabbat we are lenient. Lastly, Mishna Brurah 313:47 equates a shtender made of pieces to a cup. Shulchan Aruch 313:6 only permits constructing a bed if it is loose. Biur Halacha 313:6 s.v. darka cites the Raavad who explains that loose means that it is so loose that it would wobble in its socket.</ref>