Translation guide
A T-square is a technical drawing tool used for drawing horizontal lines and as a guide for triangles. In Japanese, it is referred to by specific terms depending on context, but the most common is a direct loanword.
The physical T-shaped ruler used in drafting and technical drawing.
The standard Japanese term for a T-square. Literally 'T-ruler'.
製図にはT定規が必要です。
You need a T-square for drafting.
An alternative term using the kanji for 'T-shape', less common than the loanword version.
古い製図室には丁字定規がまだあります。
In the old drafting room, there are still T-squares.