one of common productions that produced from springy rod are structure of mattresses. usually, three sizes of rod are used.
4mm rod as length for round frame: when somebody sits on edge of mattress, mattress is exposed by high pressure. however, when he sleeps on it, weight is distributed, so mattress is exposed by less pressure. as a result we need stronger and thicker length for frame.
- 2or 2.2 mm rod for bonnels
- 1.4mm rod for stitches of bonnels
