if you are looking to get an equal border around your image, try this trick...
(for best results, have the grid showing)

click the first point where you want the line to start.
press "shift" and the click where the end of the line will be, release "shift.
this draws a straight line.
I think if you press "shift" again, and the next point, it will do another line.
keep doing this until your border is complete.

Hope this helps you with what you are trying to do.
If not, let us know and we'll try something different.

__________________
Colleen in Friendly Manitoba...
Proudly selling digital designs at SBB
(Come take a peek at my Gallery or check my BLOG to see what I'm up to)