Need help finding a specific Google Maps related website

I want to draw a 35m x 15m rectangle (to represent a building's footprint) on Google Maps then drag it around within the property's boundaries. I'm sure there used to be a website where you could enter dimensions that would allow users to do the above, possibly using Javascript to create the rectangle overlay? Anyhow can't find it now so $10 to the first person who can post a link to a website that has this facility.