[Therion] extend vertical command

Hello I have seen an instruction in an therion exemple in the web site ( I cannot find the url now) saying we can put vertical a survey (not compleatly vertical) in an extended scrap. This instruction is put in a centerline extend vertical n15 n16 But I cannot find it in the thbook.pdf, and it seems to not work in the last therion release. Does it still work or not ? My problem is that the drawing of my climbing pit seems to be to larg as my survey go rigth to left in the pit. so the scrap drawing is to large instead of been thin (and high). Thanks. Gilbert