An older couple was sitting on the porch in their rocking chairs watching the sunset. The older woman picke up her cane and whacks the guy across his legs. The man says, " What the hell was that for?" The woman replies, " That was for fifty years of bad sex." About ten minutes later the old man picks up his cane and whacks the old woman across her legs. The old woman asks," What was that for?" The old man says, " For knowing the difference!"