Alternatively, make an 'L' shape with two lines and group it. Draw a square
for the moment and specify No Fill. Position it where you want then move the
'L' to one corner such that it looks like a continuance of the sides of the
square. Copy/paste the 'L' and rotate left (or right) and move this new 'L''
to another corner. Repeat unitl all four corners are done then delete your
square.
I hope this makes sense (and helps!)