Square Huiito

It writes the Japanese word for feet in a square cell.

The four Japanese syllable characters in フィート fit inside one square text cell. 組文字 (characters arranged together) let print fit longer terms into tight spaces, including newspapers, legal documents, and forms.

When should I use ㌳?

Use it when the compact Japanese layout matters.

For ordinary writing, フィート or ft is clearer. In vertical Japanese text, a font may arrange the characters inside ㌳ differently from their horizontal layout.