Variable Capacitor, Help Please.

Can anyone help me please?

I am building a simple FM transmitter, the circuit diagram can be found here:-

Free Kit Plans - Build your own FM Transmitter

I could not get the type of variable capacitor listed and instead have a dielctric film trimmer type (I believe). This has 3 pins on it whereas the one in the diagram has two.

Does anyone know what the third pin is for and what I should connect it to?

Any help would be very gratefully received.

Two of the pins are the same connection, it's just an extra mechanical mounting point.

Thankyou so much for your help.
I'm am about to try that link to find which pins are which. At least the part is O.K. and I can build it now.
Cheers.

You don't need a link to show you that two pins are shorted together.
You just need to measure the 3-pins variable capacitor with an ohm-meter.