Definition of side-lock:
(n) :
A bounding straight edge of a two-dimensional shape.
(n) :
A flat surface of a three-dimensional object; a face.
(n) :
One half (left or right, top or bottom, front or back, etc.) of something or someone.
(n) :
A region in a specified position with respect to something.
(n) :
The portion of the human torso usually covered by the arms when they are not raised; the areas on the left and right between the belly or chest and the back.
(n) :
One surface of a sheet of paper (used instead of "page", which can mean one or both surfaces.)