Any home handyman or woodworker that has built cabinets, picture frames, doors or other square and rectangular items knows the value of making them perfectly square. Creating true 90 degree angles is much easier said than done.
3 - 4 - 5 rule
The 3-4-5 rule can be applied to any cabinet or other item that you are making that needs to be as perfectly square as possible. The 3-4-5 rule guarantees a perfect 90 degree corner.
In practice to use the 3-4-5 rule all you have to do is ensure that the diagonal distance measured in both directions across the face of the cabinet or corner to corner on an item such as a cabinet frame are identical, as shown in Figure 1.
In practice there are two problems associated 3-4-5 rule.
Figure 1 - 3-4-5 Square rule
- How do you physically measure the diagonal. Holding the tape measure in place can be a very difficult process to perform.
The following video identifies the problem of actually performing the diagonal measurement as well as providing a solution to the problem.
If you make a lot of items that need to be squared you should consider the purchase of Square Checks for tape measure ends, as shown in Figure 2.
Figure 2 - Square Check for tape measures
These inexpensive Square Check tape measure ends will ensure that diagonal measurements made on cabinets and other items are always taken accurately, as shown in Figure 3.
Figure 3 - Square Check being used on cabinet
- Once you have verified that the diagonal measurements are identical, how do you ensure that the cabinet or other item does not shift out of square as you glue and/or fasten the joints together.
One of the easiest methods to ensure that the cabinet or other item that you are making does not go out of square is to use a Clamp-It® assembly square on the corners, as shown in Figures 4 through 7.
These plastic right angles, available in a variety of sizes and set configurations ensure that the cabinet remains perfectly square while the glue dries and/or while you are inserting fasteners.
The Clamp-It® will even make sure that joints made with dowels or biscuits remain square as glue dries.
Figure 4 - Clamp-It® being used on cabinet
Figure 5 - Clamp-It® being used on shelf
Figure 6 - Clamp-It® being used on drawer