fits well across the deck - you do need to have bungies - a clip on each corner would help if you were intending to secure to deck lines but this is a killer way to waterproof your map at an inexpensive price.
When I first got it in the mail it looked like a glorified zip lock bag with hooks attached. I still think it is but worth the money because I can not figure out any other way to attach a zip lock bag to my boat. It is really nice to have a map handy when you are trying find land mark or geographical features to figure out where you are. It is also really great for hiking for the same reasons.