How about the woman pulls out a large screw driver, then waves it at him saucily and indicates the uncompleted cupboards.
He smiles back saucily takes the screw driver.
And stabs her to death with it bloodily.
Before methodically assembling the cupboards and stuffing her corpse in them.
Then the police turn up find the corpse, he folds his arms and proudly says
"I did that."
Here's a rewrite with Sunsheeeeeeine's ending.
Int. Kitchen. Night
A man and woman - both dressed in going out gear - are drinking coffee at a table and gazing into each others eyes.
Man:
I'm guessing you didn't invite me back here just for coffee.
Woman:
(COY) Whatever gives you that idea?
Man:
Oh, I don't know. Something you said in the taxi about doing it in the kitchen.
Woman:
Well, if you think you're man enough...
Man:
There's only one way to find out...
Woman:
Ok! Let me just get something!
The woman goes over to some drawers and rummages about.
Man:
It's ok, I've got one here.
The man starts rummaging through his wallet. He pulls out a condom.
Woman:
(LAUGHS) That's not going to be much use, is it?! No, you need one of these.
The woman produces a large screwdriver from the drawer. The man looks confused.
Man:
What's... what's that for?
Woman:
How else are you going to put the shelves up?!
A set of shelves and fixings are revealed on the worktop.
Woman:
Okay! Right, I'm off to bed! Oh, and feel free to sleep on the sofa! Night!
The woman starts to leave the kitchen.
Man:
Shelves? I thought we were going to... you know... sex.
Woman:
No, it's not sex I want! It's shelves! I just love extra storage space. Cannot get ENOUGH of it! Put 'em anywhere you like on that back wall.
The back wall of the kitchen is revealed and shows numerous shoddily put up shelves.
ENDS
Its a no from me. 
sorry
Oh dear, Marc. What about my other alternate ending where she says her husband provides all the sex, but is useless at DIY and lends the man a spirit level?
I tink it is too mannered with the 'It" and the 'sex',that's the jokoid, you need to work it into a sketch and make it cleverer.
Heres some dialogue from a Doctors script.
LUCY: Would you like to come in for coffee.
ADAM: I'm sorry I don't like coffee
LUCY: THat's Okay I haven't got any.
ADAM: Then I would love some.
I think it needs to be a bit quicker. less on the nose if you know what I mean.
This needs more than an Allen key to fix it!
Have you rang 'Screw Fix Direct' they could have a punch line over to you the next working day, it's free delivery as well!
NB
Word of caution don't let them drop 'Plumb Bob' on you, he's a straight man and will only make matters worse if that's possible.
Quote: Ben @ October 7 2012, 9:42 AM BSTOh dear, Marc. What about my other alternate ending where she says her husband provides all the sex, but is useless at DIY and lends the man a spirit level?
The whole DIY thing just seems too predictable and ordinary. Needs a bigger left turn.
How about this f the cupboard leads to narnia?