Reference for Beitzah 4:6
רַבִּי אֱלִיעֶזֶר אוֹמֵר, נוֹטֵל אָדָם קֵיסָם מִשֶּׁלְּפָנָיו לַחֲצֹץ בּוֹ שִׁנָּיו. וּמְגַבֵּב מִן הֶחָצֵר וּמַדְלִיק, שֶׁכָּל מַה שֶּׁבֶּחָצֵר מוּכָן הוּא. וַחֲכָמִים אוֹמְרִים, מְגַבֵּב מִשֶּׁלְּפָנָיו וּמַדְלִיק:
R. Eliezer says: One may take a wood splinter from before him [i.e., from what is before him in the house] to pick his teeth with. [Not necessarily "from before him," for according to R. Eliezer it is even permitted to take one from the courtyard; for he says: "Whatever is in the courtyard is 'prepared.'" "from before him" is stated because of the rabbis, who differ with him, saying that even from before him — to kindle, it is permitted; to pick (his teeth) it is not permitted, the rabbis holding that wood may be used only for kindling.] And he may collect (wood) from the courtyard and kindle it, for whatever is in the courtyard is "prepared." And the sages say: He collects from what is before him and kindles, [but not from the courtyard. For since splinters are thin and it is difficult to gather and collect them, they did not "stand" for this from the day before. As to your saying: "He may take a splinter to pick his teeth with," we (the rabbis) hold that even from before him he may take wood only for kindling, wood being permitted only for that purpose. They differ in both instances, and the halachah is in accordance with the sages. It is permitted to take a pick for one's teeth only from the manger, and he may not cut or fashion it for this unless it is fit to be eaten by an animal. For anything which is fit to be eaten by an animal may be cut both on yom tov and on Shabbath and is not regarded as "fashioning a vessel."]