Why Do Some Screws Have Square Holes?

If you’ve ever opened a toolbox or started a home DIY project, you might have come across a screw with a square hole in its head. Unlike common Phillips or flathead screws, these square-holed screws—also known as Robertson screws—have a unique design. But why do they exist, and why are they used? In this article, we’ll break it down in simple words. Whether you’re a curious homeowner, DIY hobbyist, or beginner, this guide will explain everything you need to know.

What Are Square Hole Screws?

Square hole screws are often referred to as Robertson screws, named after their Canadian inventor, P.L. Robertson. These screws have a square-shaped socket in the head, which fits with a square-tipped screwdriver or bit. The design is precise and practical, often preferred in woodworking and construction.

The History Behind Square Hole Screws

The square hole screw was invented by Canadian toolmaker Peter Lymburner Robertson in 1908. He created the design to prevent the tool from slipping out of the screw head—a common issue with flathead and Phillips screws. The design quickly became popular in Canada due to its efficiency and safety.

Interestingly, although Henry Ford considered using Robertson screws in his Model T assembly lines, a licensing disagreement prevented the widespread use of these screws in the U.S. However, in Canada and other parts of the world, they have remained a top choice in various trades.

Why Do Screws Have Square Holes?

So, what’s the point of a square hole in a screw? Here are several practical reasons:

1. Better Grip with Screwdrivers

The square socket holds the screwdriver tip firmly in place. This reduces the risk of slipping, which can strip the screw head or damage your project.

2. One-Handed Operation

Square screws are known for staying on the screwdriver even before you begin driving them in. This feature is handy when you only have one free hand.

3. Less Stripping

Because of the tight fit between the screwdriver and the screw head, there’s less chance of the screw getting stripped. This is especially helpful in hard materials like hardwood or metal.

4. Efficient for Power Tools

Square hole screws work great with electric screwdrivers and drills. They allow fast driving with minimal cam-out (the tendency for a driver to slip out of the screw head).

5. Durability and Strength

Robertson screws are durable. The square hole provides a large contact area between the tool and the screw, distributing torque evenly and reducing wear.

Common Uses of Square Hole Screws

You’ll find square hole screws in many areas, including:

• Woodworking: Cabinet makers, furniture builders, and carpenters often prefer these screws.
• Construction: Builders use them for framing, decking, and subflooring.
• Electrical Work: Some electrical boxes and devices come with Robertson screws.
• Automotive: In Canada and select countries, square hole screws are used in vehicle manufacturing.

Comparing Square Hole Screws to Other Types

Let’s compare Robertson screws with other popular screw types:

Screw Type	Pros	Cons
Flathead	Easy to find	Easy to strip, not ideal for power tools
Phillips	Common, decent grip	Can cam-out under pressure
Torx (Star)	Excellent grip, anti-cam-out	Less common, needs special bits
Robertson	Strong grip, anti-strip, power tool-friendly	Not as common in all regions

Types of Screwdrivers That Fit Square Hole Screws

To work with square hole screws, you need the right tool. These include:

• Manual Robertson screwdrivers
• Square drive bits for drills or electric screwdrivers

These tools often come color-coded by size (e.g., red for #2 Robertson), making it easy to grab the right one.

Tips for Using Square Hole Screws

1. Pre-Drill Pilot Holes: This helps prevent the wood from splitting and makes driving the screw easier.
2. Use the Right Bit Size: Mismatched bits can damage the screw head.
3. Avoid Overtightening: Even though square screws are durable, excessive torque can still cause damage.
4. Check for Magnetic Bits: These help keep the screw on the bit, especially useful for overhead work.

Are Square Hole Screws Better for DIY Projects?

In many ways, yes. Square hole screws offer benefits like easier handling, better grip, and fewer stripped screws. They’re ideal for:

• Shelving
• Cabinets
• Deck building
• Framing
• Indoor and outdoor woodwork

If you’re just starting out with home projects, using square drive screws can make your life easier and your results more professional.

Are Square Hole Screws Available Everywhere?

While square hole screws are very popular in Canada, they’re not as common in the U.S. and other countries. However, with the rise of online shopping and global DIY trends, they are becoming easier to find. Many hardware stores now stock them, and they’re readily available on websites like Amazon, Home Depot, and Screwfix.

Conclusion: Should You Use Square Hole Screws?

Absolutely. If you’re looking for a screw that offers strength, ease of use, and less chance of slipping or stripping, square hole screws (Robertson screws) are an excellent choice.

Whether you’re hanging a shelf, building a deck, or fixing a chair, choosing the right screw can make a huge difference. Give square hole screws a try in your next project—you might never go back to Phillips again!

Final DIY Tip

Keep a variety of screwdriver bits in your toolbox, including square drive bits. You never know when you’ll come across a Robertson screw, and having the right tool on hand will save you time and frustration.

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