Bone, enough to make a spoon. R’ Yehudah says: Enough to make with it a tooth [of a key]. Glass, enough to scrape the point of a weaver’s needle. A pebble or stone, [large] enough to throw at a bird. R’ Eliezer bar Yaakov says: [Large] enough to throw at an animal.

A shard, [large] enough to place between one board and another — [these are] the words of R’ Yehudah. R’ Meir says: [Large] enough to pick up fire therewith. R’ Yose says: [Large] enough to contain a quarter-log. Said R’ Meir: Although there is no proof to the matter, there is an intimation of the matter: And there shall not be found among its pieces a shard with which to pick up fire from the hearth (Isaiah 30:14). R’ Yose retorted: Is there proof from there? [The verse concludes,] Or to scoop up water from a pit (ibid).