Constructed from sturdy solid cedar, the Mason Bee Castle is home for a ten layer Quick Lock Stacking Tray (included). The wooden predator guard slides in from the bottom, and is secured in place by a fastening device. The Castle includes a simple but sturdy mounting bracket and space inside to place overwintering mason bee cocoons. It provides safe nesting sites for up to 60 female mason bees for improved pollination for berries and fruit trees. Were they to fill all the holes, it would produce 360 mason bee cocoons for pollination the following year.