A t-square is the basis of hand drafting. Nice tools can be a difference between an enjoyable experience and frustration mixed with misery. I’m not the originator of the t-square of course, but this is my edition of it. I was dissatisfied with versions that were commercially available. Even the second hand, older ones in the U.S. were not appealing because of low quality. Your availability may differ.

The two parts I didn’t like about the available t-squares are the weight and adjustability. The commercial ones are really lightweight. I don’t see any benefit to a lightweight t-square unless one was carrying it far distances. A heavier t-square will help it stay stationary while using it, as well as enabling hardier construction. Often using staples, they also didn’t seem to come with any adjustablility for making the unit itself square. It technically isn’t necessary as one aligns the paper to the square to use it.

Construction parts on mine are oak wood and aluminum because I have expensive tastes. Use whatever material you have available. The aluminum needed a clear coat so as to not rub on the paper. The longer horizontal portion should preferably be a composite of some sort, as a long piece of grained wood will curve with the humidity. The vertical end can be anything fairly stable. If using wood, use the straightest grain you can find that is stable and seasoned. Put a hole in the end of your horizontal for hanging.

For binding the two parts, I created a aluminum backer and tapped/threaded for 4 stainless steel bolts. That’s optimal for durability, albeit a little overkill for a t-square. Satisfactory is 4 pan head screws with good threads on them. What gives the unit adjustability is over-sizing the holes on the horizontal. In my case the long aluminum part. They are slightly over-sized to allow alignment and squaring of the unit.

To square an adjustable t-square you need a table with 2 parallel sides, pencil and paper. Put the t-square on one side of the table and draw a horizontal line. Put it on the other side of the table and draw a horizontal line connecting to the first one. They probably made an X on your paper rather than being able to make a continual line. Adjust the square until you can make a continual straight line. Now its square.

I squared mine with a framing square, aligning it to both sides of the t-square. It’s a pain because the commercially available framing squares here are off. So you need an even quirky gap on both sides with aligning the t-square that way. You can fix your framing square with the paper line method as well. Sand or file the high spots on the framing square, as it has no adjustments.

There is an option of hollowing a retainer for shapes or angles in your t-square. Another possibility is cutouts with measurement scale markings. Just don’t put numbers on the scale marked on the t-square, then count the markings for distance/length while using it.

Basic pieces to make or acquire:
Pencil
Standard paper
Masking tape
Basic ruler
30/60/90 Triangle
45/45/90 Triangle

Upgrades to consider:
Architectural ruler
Mechanical ruler
Larger paper
Drafting tape