The Poskim discuss whether it is permissible to use a plunger to unclog a sink or toilet on Shabbat. The consensus of Hacham Ovadia and Hacham Bension is to prohibit doing so. Hacham Bension even implies that it may be an Isur D’oraita-a Torah Prohibition, since the sink and toilet are connected to the house and ground, it may constitute a violation of Boneh-constructing. Nevertheless, he allows instructing a non-Jew to perform the operation, since it involves Kavod Habriyot-human dignity and is a source of significant suffering.
The Shemirat Shabbat K’hilhata (R. Yehoshua Y. Neuwirth, Jerusalem, 1927-2013) allows pulling apart a pair of new socks which are attached by the plastic thread. Doing so is not considered Tikun-the finishing act of forming the socks. They already exist independently and were only attached to prevent them from being separated.
Similarly, he permits removing the pins in a new shirt. They are only placed there to keep the creases in place; this is not considered finishing the garment.
The Poskim also discuss whether it is permitted to lace a shoe on Shabbat. Hacham Bension and the Menuhat Ahaba (Rabbi Moshe Halevy, Israel, 1961-2001), concur that the Halacha depends on whether it is the first time the shoe is being laced. In a new shoe, the first lacing is considered part of the completion of the shoe, and is therefore prohibited. In an old shoe, which has been laced previously, it is not considering a finishing act.
It is prohibited to use a plunger to unclog a sink or toilet on Shabbat.
It is permitted to pull apart a pair of new socks and to remove the pins in a new shirt.
It is prohibited to lace a new shoe, but it is permitted to lace a shoe that has been laced previously.