Sometimes in their haste to return their reply card for your wedding, a guest will forget to fill in their name. This leaves you stuck with the headache of trying to figure out which person that particular card belongs to.
To remedy this, assign a number to each guest and then write that number on the lower corner of the back of the corresponding reply card before you mail out your invitations. Then, if you receive a card sans identifying information, you’ll be able to figure out which guest it belongs to quickly. I’ve always hated how tacky and conspicuous even the smallest numbers look when written in pencil or pen, so I recommend using an invisible ink or black light pen so as not to detract from the look of your invitations.