Continuity mistake: Monk and Natalie question the landlady, Sylvia, about the missing guest. Every time the camera angle changes, Sylvia's arms change from being crossed in front of her to hanging loosely at her sides.
Continuity mistake: When Natalie and Al are struggling, the gun lands on the table and there's a basket of corks. Somehow when Al gets the gun, the basket is tipped over and the corks are on the table. But after Monk hits Al, the corks are all back in the basket, which is upright.
Continuity mistake: When Monk and Al are sitting to drink wine, Al grabs his bottle with one hand to pour the wine and the other hand is hanging down to his side. In the next shot, as he's pouring the wine, he's holding the glass with the other hand. In the next shot, his hand is by his side again.
Answer: Notice also that in the opening credits scene when he is touching parking meters her also wipes his hand on his clothes each time he does it.