Good comment drew - have two stacks of your cards out. People pick them up and may call you later.
Another suggestion is one on attitude:
If you are there to sell knives, your attention is to the people on the other side of the table. Stand up if someone stops to look, stand up and say, "Hello". Tell them to feel free to pick one up for a closer look, and you will be glad to answer any questions. Smile at everyone, and treat the lookers just like the buyers.
The folks who sit in their chair and chat with a friend are usually the ones who say they had a terrible show. It is a rare case where a customer says, "Excuse me, but if you have the time I would like to buy this knife!"