The two Sig buttons behave identically except for the preference settings you give them. Choose Sig 1... or Sig 2... from the Preferences menu; the Signature Preferences dialog will appear. It allows you to specify the text to be inserted in the clipboard when a Sig button is clicked.
The window has room for 79 characters across, by 6 lines down. (It would have been 80 characters across, but there isn’t quite room for 80 characters on the smallest Macintosh screens.) Enter as little or as much text as you like. If you need to enter more than six lines of text, you may want to compose the text in a word processor or text editor, copy it, then paste it into the Signature Preferences window. (Note: for technical reasons, the Edit menu is disabled when the Signature Preferences dialog is displayed. You can still cut, copy, and paste text in the dialog by typing ⌘X, ⌘C, and ⌘V as usual.)
The buttons are called “Sig” buttons because most people use them to paste in their e-mail or network signature. These signatures (often called “.sigs” or “dot-signatures”, from Unix terminology) usually contain your name and your e-mail address. Mine looks like this:
-- Rick Holzgrafe
Semicolon Software
rmh@taligent.com
...but you can enter any kind of text you like. You can include your postal address along with your e-mail address; or the slogan of your company; or a bit of poetry or a joke or a motto that you enjoy and want to pass on to others. (But remember: some people must pay to download every character, and others may have slow modems. It’s considered polite to keep your signature short and to the point.) Of course, you can also enter text that’s not a signature at all, if it’s something that you find yourself typing over and over again.