Spacers and standoffs are often needed to mount printed circuit boards in an enclosure or to stack circuit boards.  Male - female threaded standoffs are the standard, but different lengths may be desirable for every situation, so it's hard to ensure that you have the right pieces when you need them.

If you use pump bottles of shampoo, shower gel or other products, you have a free supply of spacers any length you need.  This type of bottle (usually) has a rigid plastic tube from the pump to the bottom of the bottle that's the perfect size for a 3mm or 4-40 screw.  Run a screw through the board, put a spacer over the screw, put the other board or panel in place and secure it with a nut.

You might be tempted to cut the spacer to length with a pair of side cutters, but this crushes the tube and leaves a ragged cut.  The tube can be cut with a utility knife, but let me tell you a secret.  There's a much easier tool to use that makes a square accurate cut quick and easy, with no risk of blood.   Dog nail clippers from the dollar store, with the curved blades, surround the tube and cut it cleanly.  Ok, I lied.  The spacers are almost free!  There are similar clippers costing a lot more, but the buck variety works perfectly.

Move the shutter that prevents cutting too deep to the side.