North Carolina Building Contractor License Practice Exam

How long must screws be to properly fasten a cabinet with a 3/4 inch backrail to 1/2 inch drywall?

1. 1 inch

2. 2 inches

3. 3 inches

4. 4 inches

The correct answer is: 2 inches

To properly fasten a cabinet with a 3/4 inch backrail to 1/2 inch drywall, the length of the screws needs to account for the thickness of both the backrail and the drywall. The backrail is 3/4 inches thick, and the drywall is 1/2 inch thick. When fastening the cabinet, the screw must penetrate through the backrail and into the wall sufficiently to ensure a secure connection without risking damage to the drywall. A screw that is too short may not reach the stud behind the drywall if that is what the cabinet needs to be anchored into. A 2-inch screw meets these requirements: it is long enough to penetrate through the 3/4 inch backrail and the 1/2 inch drywall, allowing for adequate grip in the structural framework behind the drywall, often a stud or blocking. This provides enough length to ensure that the cabinet is securely mounted to the wall while still being manageable and not overly long, which could cause problems with clearance or structural integrity. Screws that are too short or excessively long can lead to issues; therefore, 2 inches is the most suitable length for this scenario, ensuring a solid and reliable installation.