Related for Shabbat 24:5

מְפִירִין נְדָרִים בְּשַׁבָּת, וְנִשְׁאָלִין לִדְבָרִים שֶׁהֵן לְצֹרֶךְ הַשַּׁבָּת. פּוֹקְקִין אֶת הַמָּאוֹר, וּמוֹדְדִין אֶת הַמַּטְלִית וְאֶת הַמִּקְוֶה. וּמַעֲשֶׂה בִימֵי אָבִיו שֶׁל רַבִּי צָדוֹק וּבִימֵי אַבָּא שָׁאוּל בֶּן בָּטְנִית, שֶׁפָּקְקוּ אֶת הַמָּאוֹר בְּטָפִיחַ, וְקָשְׁרוּ אֶת הַמְּקֵדָה בְגֶמִי, לֵידַע אִם יֵשׁ בַּגִּיגִית פּוֹתֵחַ טֶפַח אִם לָאו. וּמִדִּבְרֵיהֶן לָמַדְנוּ, שֶׁפּוֹקְקִין וּמוֹדְדִין וְקוֹשְׁרִין בְּשַׁבָּת:

It is permitted to annul vows on Shabbat [a husband, his wife's vows; a father, his daughter's], and it is permitted to consult [a sage (for absolution of vows)] for things which are needed for Shabbath, [as when he vowed that he would not eat that day. This ("things which are needed for Shabbath") refers specifically to consulting a sage; for a husband or a father may annul both vows which are Sabbath-need related and those which are not, for he can annul them only on the day that he hears them. And with vows which are Sabbath-need related, even if he had time to consult a sage about them before Shabbath, he is permitted to consult him on Shabbath.], and it is permitted to stop up the maor [the window by which light enters, with a board or anything else used for that purpose], and it is permitted to measure a cloth [If it came in contact with something unclean and then with clean things, it is measured to determine whether or not it is three by three fingers. For a cloth less than three by three neither acquires nor transmits uncleanliness.], and (it is permitted to measure) a mikveh [to determine whether it is one by one cubits and three cubits high. For these are measurements of mitzvah, for which reason they are permitted on Shabbath.] And it happened in the days of the father of R. Tzaddok, and in the days of the father of Abba Shaul b. Batnith that they stopped up a maor [a window, called a "maor" because light (orah) enters through it] with a tafiach [an earthenware pitcher] and tied a mekeidah [an earthen vessel] with gemi (reed-grass) ["gemi," specifically, for, being fit for animal food, it is not voided (to the vessel) as a permanent knot] (they tied it, etc.) to determine whether or not there was a cleft of a handbreadth in the gigith (the basin). [There was a small path between two houses, which was not roofed, but over which a basin was inverted. There were windows which opened from the houses to the path, and they feared lest someone die in one of the houses and the tumah (dead-body uncleanliness) go from the window to the path and from the path to the other house by way of the open window. They, therefore, stopped up the window facing the house of the tumah with a tafiach with its back to the path (an earthenware vessel not acquiring tumah from the back and thus serving as a partition against tumah). For they feared that the cleft in the gigith might be less than a handbreadth, in which instance the gigith would "tent" the path and the uncleanliness would come by way of the path from one house to the other. Afterwards, they had to open the window and take out the stopper, and they wanted to determine whether the cleft in the gigith were a handbreadth (or more) — in which instance there would not be a tent in that path for the conducting of the tumah, for the tumah would leave the path upwards by way of the cleft in the gigith — or whether it were less than a handbreadth, in which instance the path would act as a "tent" and conduct the tumah from house to house. They, therefore, measured a mekeidah, tied it with gemi, and extended it to the top (of the gigith) to see whether or not the cleft were a handbreadth.] And from what they prescribed we learned that we stop up, and measure, and tie on Shabbath [so long as it not be a permanent knot and the measurement be for mitzvah or to the end of a halachic ruling.]

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