On twitter a while back @SimGuruGraham shared this image and asked us to guess what it was.
Most people guessed first hand controls on the houseboats. NOT EVEN CLOSE!
While placing a house from the house bin on a lot that is too big, it would be placed in the middle with a lot of space left on the sides. These controls allow you to move the house to sides of the lot.
Yes. You can move the house around on the lot. You can only do this while placing the house on the lot, after that it is stuck in position.
Mostly on the land.
@Simsnieuws found this hidden gem, I confirmed that it works for all houses and houseboats that you place from the housebin.
Much love to The Sims team for this.