Halakhah zu Bereschit 49:8

2 Masekhet Soferim has different definitions: a petuha is anything which does not start at the head of the line. A setuma is anything that stops in the middle of the line. How much must be left at the beginning of the line for it to be called a petuha? Enough to write a word of three letters. How much must be left in the middle of the line for it to be called a setuma? Enough to write a word of three letters. [End Masekhet Soferim quote.] Suppose he finished a paragraph at the edge of the page and started a new line, and left enough space at the beginning of that line to write three letters, and then started to write? Come and learn from the two sources; the baraita gives the essence of the issue. The baraita reasons that the beginning of the line is what determines a petuha, not the end of the line [so the example case is a petuha according to the baraita]; if one leaves a gap at the beginning and also at the end of the line, it is still a petuha. But the old siddur reasons that it is the end of the line that determines a petuha, not the beginning of the line [so the example case is a setuma according to the baraita]. [To avoid ambiguity, therefore...] if he makes a petuha with space both at the end of the line and at the beginning of the line it is good for both of them. This is correct. There is also another order of petuhot and setumot which seems entirely unconvincing. And these are the tagin of a sefer Torah and the petuhot and setumot according to the masoretic tradition. ביה שמו: the following words should be placed at the beginning of a line and the top of a column: Bereshit (Gen. 1:1); Yehudah ata yodukha (Gen. 49:8); Haba-im ahareihem bayam (Ex. 14:28); Shemor ve-shamarta (Deut. 12:28); Motza sefateikha (Deut. 23:24); Ve-a'ida bam (Deut. 31:28).