House Wrens Kits are fun and educational projects for families. Because the smaller House Wren prefers multiple cavities for the male to "fill" with sticks to show off to the females, kits are an inexpensive way to add more houses to your yard. Their boxes should have a hole with a diameter of about an inch but no larger than 1 and 1/8 of an inch. House Wren houses can be free swinging or firmly mounted.