The ledger is a critical part of your new deck. It attaches the deck to your house and it is also provides the reference point for laying out the deck. Because of its importance, the ledger must be correctly positioned and fastened very securely to the house. Be sure that you use pressure treated lumber for the ledger. Some things that you should consider is that the ledger should be installed at least one inch below any doors that opens out onto the new deck to prevent water, ice, and snow to from leaking on the bottom door seal.