Shabbos 13:4

The amount of wool that would render one liable for bleaching, combing, dyeing and spinning is twice the distance between a spread thumb and forefinger. If a person weaves two threads, he is liable for the distance between a spread thumb and forefinger.

Shabbos 13:5

Rabbi Yehudah says that if a person traps a bird in a tower or a deer in a house, he is liable; the Sages add trapping in a courtyard or an enclosure. Rabban Shimon ben Gamliel says that not all enclosures are the same. The general rule is that one is exempt for incomplete trapping and liable for complete trapping.