Falkirk Wheel doors and seal in 4 stages. Left side of each photo is caissons door. Right side is lower canal basin door. From left to right: doors aligned but with a gap, u-shape seal extended, water filled, and doors lowered.
<a href="//commons.wikimedia.org/wiki/User:Z22" title="User:Z22">Z22</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>