Lock mechanism

A lock mechanism, comprising:

• two plate-like lock piece portions provided respectively at first and second members and juxtaposed to each other substantially in a common plane when locking said first and second members together;
• engagement grooves formed through said lock piece portions in a direction of a thickness of said lock piece portions, and said engagement grooves having openings formed respectively in end surfaces juxtaposed to each other and facing in the same direction;
• and
• a lock ring of a square-loop shape having opposed straight portions to be fitted respectively in said engagement grooves in said lock piece portions to interconnect said lock piece portions,
• wherein when viewed in the direction of the thickness of said lock piece portions, each of said engagement grooves has an L-shape defined by an introduction groove portion extending from the opening in a direction substantially perpendicular to the end surface, and a slide groove portion extending from an inner end of said introduction groove portion in a direction substantially parallel to the end surface;
• wherein said introduction groove portion in said lock piece portion of said first member has a first holding portion for rotatably holding the straight portion of said lock ring;
• and
• wherein at least one of an inner end of said slide groove portion in said lock piece portion of said first member and an inner end of said slide groove portion in said lock piece portion of said second member has a second holding portion for holding the straight portion of said lock ring.