There is a custom to buy a knife for Rosh Hashanah: the qualifier is that the knife not be serrated. What is the source for this custom and what is the significance of the knife not having edges?
"Chatach," (חתך), which means "cut," is the name of the angel in charge of livelihood.
Consider that the final letters of the Hebrew words, פותח את ידך, "You open up Your hand" (Psalms 145:16), spell "chatach." Additionally, the word that follows in the verse, "u'masbe'a" – "and satisfy [the desire of every living being]" has the numerical value of 428 – the same value as the word "chatach."
For this reason, purchasing a new, sharp knife is a segulah (spiritually propitious), for livelihood, which we petition from G‑d for the upcoming year.
Nitei Gavriel 11:10