Use a straightedge and sharp blade to get clean, straight lines.
The shroud lines are old and have bends.
Run an iron over the lines with the iron on a dry, cotton setting.
TIP:
NEWBIES:
Try not to touch any stickers. The oils on your fingers could diminish the adhesive. Here I've lifted the reinforcement ring with my knife. Center and position with the sticker still on the blade.
To prevent a tear from starting, punch the hole up against the outside edge of the ring. Rotary punches work great but you've got to have cardstock behind the sheet when punching through the plastic.
Shroud lines can be hard to tie.
TIP: Use long tweezers to tie the knot. On shroud lines, I use a simple square knot.