toggle switch
Toggle switches are frequently attached to a mounting surface with a nut that has two indentations on opposite sides.
I usually use needle nose pliers. They work, but sometimes mar the fastener.
If it's a "reed switch" you're talking about, they do indeed exist in SPDT form, though they're not as common as SPST N.O.. Also in SPST N.C. (normally closed) form. For example:
If you want to reverse the action of a SPST N.O. switch, you may be able to do something like this:
In the case of the BJT, make Rx about 10-20 times RL. In the case of the MOSFET, make Rx a few K ohms.
simulate this circuit – Schematic created using CircuitLab
Your diagram shows SPDT, so that's what you need. SPST isn't going to work.
The peak current through the switch will be the same as if you connected the relay coil directly to the 12V supply without the capacitor in place. (The capacitor merely causes the current to decay down to zero from this peak value.)
Therefore, if your 12V relay has a coil resistance of 400 Ω, the peak current will be 12V/400Ω = 0.030A.
With a 220 µF capacitor, the relay will activate for roughly 50-100 ms each time the toggle switch changes state. The exact value depends on the holding-current requirements of the relay.
Best Answer
I've always known them as slot or slotted nuts (a type of castellated nut) although I did come across a reference to switch nuts, which makes sense if they are used to fasten switches.