Freeformed Astable Multivibrator

If you're powering a project from a 9V battery, you can salvage a suitable connector from a dead 9V.

Grab your bucked of dead batteries and search through it for 9V

Choose one that doesn't have a buildup of blue corrosion on it

Remove the sheet metal case being careful not to cut yourself. This battery has flat cells in it, but occasionally you'll find six cylindrical cells. There will always be six of them because each cell adds 1.5V to the overall output.

Liberate the connector for your own purposes. Soldering wires to these can be a challenge. I recommend roughing up the surface first with a dremel or coarse sand paper and adding a blob of solder before trying to connect a wire or component lead.