What does "proper right" mean?

The direction which is to the right from an object's perspective, the direction 90 degrees clockwise from the front.

Proper right

noun

noun ·Rare ·Advanced level

Noun

1
The direction which is to the right from an object's perspective, the direction 90 degrees clockwise from the front. uncountable
"Sennit for Hats […] always join on the upper side, because the under side is the proper right side of the sennit."

"Sennit for Hats […] always join on the upper side, because the under side is the proper right side of the sennit."

proper (in the sense of "its own") + right; from Latin proprius.