A signing frame will involve a picture of you, normally, or it can be a picture of your rings, and in fact anything you want it to be. This is mounted in a wide, plain white board mount. For the wedding reception you would (carefully!) remove the glass and keep that somewhere safe, and mount the frame somewhere in the venue, perhaps in an easel, where your guests can get to it easily to sign it with their names and a message for the day. What you must NEVER do is use a normal Biro as in daylight, over time, this will fade to a nasty pale grey. Always use fade resistant ink, or to be be ultra safe, a “bog standard” HB pencil.
After your wedding day you simply replace the glass, and perhaps replace the image with your favourite wedding photo, and hang it on the wall somewhere with pride of place for all to see and share. A lasting record of your treasured guests, and the warm feelings and greetings that they shared with you.