(Mishnah): One partner can only force the other to divide a courtyard if each will receive 4 amos.

For a field, each must receive 9 kavs.

R. Yehudah: Each must receive 9 half kavs.

For a garden, each must receive half a kav.

R. Akiva: Each must receive a Beis Rova (an area in which one plants 1/4 of a kav, which is roughly 146 square amos.)

For palaces (each must receive a palace), for a dovecote, for a garment, for a bathhouse, for an olive press; each must receive a size that is big enough that it still has the same name as before.

When is this? When they do not both agree to divide it, but if they do, they could even divide a smaller amount.

Holy writings may not be divided even if they both agree.

(Gemara) - R. Yochanan: When they said 4 amos of a courtyard, this excludes the 4 amos in front of any doorway.

Support (Beraisa of Bar Kafra): One partner can only force the other one to divide if each will receive 8 amos (4 amos in front of his house and 4 amos of the courtyard).