I used to install deck ledgers over pressure-treated spacers that I ripped on site and flashed to the siding. The space kept the ledger from rotting, but the spacers took some time to cut and install. Fortunately, two new products make the job a lot easier. The Flash Block is a 1/2-inch-thick aluminum spacer that you can sandwich between the ledger and the siding. Its diamond shape permits easy water runoff, and an offset 9/16-inch-diameter hole (large enough for a 1/2-inch bolt) ensures that the Flash Block hangs plumb during installation. Suggested retail prices are $1.99 for the 5-inch-long blocks and $2.59 for the 7-inch ones. They're available at some lumberyards, or you can order directly from the manufacturer. Contact: The Flash Block Company, P.O. Box 14, Junction City, CA