Cutting upholstery weight Linen

[pat]

Hi: Its been a long time since I've needed this kind of help. I have 30 yards of expensive linen to put on a large sectional, Have taken a t-square, chalk, made a straight line, cut it with sharp sizzors,  ended up with a uneven line. I have heard you use masking tape. Does anyone have any other tips for this dilemma. I really do not want to spend all the time masking out all the pieces that go into this very large sectional.  Thanks to all PAT 

[Mike]

it sounds like the material streached  id use a straight edge and try those rotary cutters  might try posting this in the general forum  . most don't look here I just happened along