BT Šab 105a(2) :הא דבעי זיי^ו^ני הא דלא בעי זייוני‏ : this refers to where he needs to write the tops of the letters with crowns, that to where he does not need to write the tops of the letters with crowns
See the entire entry for zyn#2 vb. D to write the top of a letter with crownlets