Sharpening knives on Erev Shabbos:
One is to beware to sharpen the [kitchen and eating] knives every Erev Shabbos, as preparing oneself for eating is included within the honor of Shabbos. In addition, [at times] one needs to sharpen the knives for the sake of Shalom Bayis [marital harmony], such as if the blade has dulled and one is unable to cut with it. [Some Tzadikim were accustomed to personally sharpen their knives using one of the stones of their home. Accordingly, some are accustomed to eat their Shabbos meals using non-serrated knives due to the above reasons, and likewise due to reasons of Kabbalah.]
One should be careful to sharpen the knives on Erev Shabbos. This is done for honor of Shabbos and for purposes of shalom bayis.
Does this law apply even today, and how practically is it to be accomplished?
Yes, the above law applies even today, and so is the custom of G-d fearing Jews. Accordingly, one should purchase a knife sharpener for the sake of fulfilling this custom on Erev Shabbos. Although the process of sharpening a knife is much simpler and easier accomplished with a non-serrated knife, it is possible to likewise sharpen a serrated knife.
 Admur 250:5; Rama 250:1; Taz 250:2; Bach 260; Rashal on Tur 260; Derisha 250:1; Beis Yosef 250 in name of Chayeh Olam [Sefer Hayirah of Rabbeinu Yona] 309; Kol Bo 31 in name of Sifri; Rokeiach, brought in Rashal and Bach ibid; Levush 250:1; Piskeiy Teshuvos 250:5
 Admur ibid; Rama ibid
The source: This is hinted to in the verse [Beshalach] “And prepare Es/that which you brought” and a knife is alluded in the word “Es”, from the wording of “Lesim Ulemizmoros” [in Yeshaya 2:4]. Thus, implying in the verse that one is to prepare the knives before Shabbos. [Admur ibid; Taz ibid; Beis Yosef ibid in name of Rabbeinu Yonah; Rashal ibid; and Poskim ibid]
 The source: This is learned from the verse [Iyov 5:24] “And you shall know that your tent is in harmony” and the Sages expounded this to be referring to the sharpening of a dull knife for the sake of Shalom Bayis. [Admur ibid; Taz ibid; Rashal ibid; Beis Yosef ibid; Kol Bo ibid; Rokeiach ibid; M”B 250:5]
 Likkutei Maharich Seder Erev Shabbos in name of Maharam Eish
 Karban Shabbos 1:7 in name of Tikkunim and Chesed Leavraham and Rokeiach; Piskeiy Teshuvos ibid footnote 22