You can use the top of an old 9V battery as a 9V battery clip for assorted
electronics projects. The "9V clip" is also used on some batter holders of
assorted voltages (ie a 4AA battery pack.)
Here's how to make a nice wire-lead version...
(This is an old idea. The only original part here is the "strain-relief" hack.
Still, new pictorials for old ideas can be pretty useful.)
Step 1: Find a dead battery...
Find a dead 9V battery. Batteries are supposed to be recycled these days,
so a good place to find dead one is at work, where they might have battery
The internal construction of 9V batteries varies a great deal, and some are
easier to convert to clips that others. Duracells are pretty good.