Buying Condoms

A young man go's to the chemist to buy some condoms, a little afraid he asks the old lady behind the counter for some.
"What size would you like?" she enquires. Unaware that there are different sizes he admits he doesn't know. The lady tells him there is a penis sizing guide in the back built into the fence, if he puts his knob through each of the holes she will be able to size it.
The lad puts his knob through the first hole the old lady grabs his knob and starts wanking it off.
The lad then puts his knob through the second hole and the lady starts sucking him off.
The lad then puts his knob through the final hole and the lady grabs it and pushes it into her arse.
After this the lady runs back into the shop and pretends to know nothing about the fence. "So what size condom do you think you need then?"
"Fuck the condoms, how much for the Fence?" the lad replies.