This is the 7th tutorial in our series of building decks. A serious, yet rewarding undertaking. If you follow the steps that we have outlined carefully and safely you should have no problems keeping your joists square and true. Joists provide the framing platform for the deck. Before you can install the joists, the ledger should be in place along the house and the girders should be secured to the posts. The joists will be anchored to the house via the ledger and then supported by the girders.