The aluminium sleeve is moved axially by the M/F selector ring on the lens. The clutch fork is attached through a small spring to the sleeve, because the dog clutch can only be engaged when the teeth are aligned.
<a href="//commons.wikimedia.org/wiki/User:Phiarc" title="User:Phiarc">Phiarc</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>