Non-Hem Tatami is a regular tatami without hem.
Ryukyu Tatami and Meseki Tatami is non-hem tatami, design characteristics of a room improves by how to spread.
Ichimatsu design, the checker board design, by putting non-hem half size square tatami in different direction with 90 degree is representative example.
The regular tatami, with hem, is sewed hem on the tatami facing which is cut with constant width. For non-hem tatami, an edge of tatami facing is sewed inward.
Appearance is slender, but strength of an edge of tatami is inferior is easy to come to spoil easily.