I put a thin magnet in the bottom, to hold the needles in place. The magnet probably came off the back of a free calendar or advertisement, meant to be stuck to your fridge. There was a bit of adhesive left, but since I was putting it into a metal tin, it didn't matter if it stuck through adhesive or magnatism. ;p
The magnet holds the needles in place and you can arrange them by height or use and they will stay how you arranged them.
One tip I learned: I put the opening of the sliding tin so that the eyes of the needles are at the top, easier to get them out, not so many pointy sharpnesses when I reach in.