They don't have to be square, or even oblong!
Here is a trapezoidal frame to display a portion of fabric which has been teased apart to expose the structure of the weave.
The frame is a beautiful pewter colour. Not as brash as a shiny silver, but more of a shiny version of the grey mount which compliments the colours of the fabric.
The cutting of the frame was interesting! Working out the angles quite took me back to school maths lessons with fond remembrance of Miss Hall. Then figuring out how to set up the mitre cutter and position the moulding correctly! Well, let's just say it took a bit of trial and error.
Trapezoidal frame anyone?