The cowboy walked into the tack shop.

"How much for a pair of spurs?"  he asked the sales clerk.

"Forty dollars."

The cowboy looked in his wallet, thought for a moment, then pulled out a twenty.

"I'll take one spur."

"What'll you do with just one?" the clerk asked.

The cowboy replied, "I figger if I can get one side of the horse movin', the other side'll go too."