The click holds the ratchet wheel against the force of the mainspring furthermore allowing the watch to be wound. The name given is well suited because the clicking noise you hear when a watch is wound is the click impacting on each tooth of the ratchet wheel. Some clicks have a separate click spring that forces it back into contact with the ratchet wheel’s teeth. Others have the spring integrated into their design. Their design can vary widely, often are a matter of architecture movement style.
For the movement to disassemble, the mainspring has to be unpowered. For this to happen, the click has to be pulled away from the ratchet wheel at the same time holding back the winding stem.
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