Wiktionary
sideless
a. Lacking a side; open at the sides
Usage examples of "sideless".
Those men too badly woundedor who were already deadwere sent to a sideless shelter at the edge of the clearing nearest the generator.
In the center of the room was a dais which was suspended precariously above a large, open well, sideless, flush with the floor.
She was dressed modestly in a plain, dark blue housedress with a sideless surcoat of dark red, but her elegance confused Anne.
The old woman shivered, wrapping her sideless surcoat tighter around her ribs.