Miszna do Nidda 6:15

Bakers’ baking-boards are susceptible to impurity, but those used by householders are clean. But if he dyed them red or saffron they are susceptible to impurity. If a bakers’ shelf was fixed to a wall: Rabbi Eliezer rules that it is clean And the sages rule that it is susceptible to impurity. The bakers' frame is susceptible to impurity but one used by householders is clean. If he made a rim on its four sides it is susceptible to impurity, but if one side was open it is clean. Rabbi Shimon says: if he fixed it so that one can cut the dough upon it, it is susceptible to impurity. Similarly, a rolling-pin is susceptible to impurity.