If you use a screw gun in your work, you'll pretty quickly accumulate a variety of bits. I keep them at hand with an old magnetic tape-measure holder. As shown in the drawing, I hook the tape-measure holder over the flap of the inside pocket on my tool belt so that the holder is partly enclosed by the outside pouch. This placement gives me ready access to the bits, and if one of them should fall off the magnet, it ends up in the pouch.
Eric Roozekrans, Great Barrington, MA