yeah, but are there (roughly guessed) 41,43 and 39 foots containers? the upper ones are larger then the lower ones on some occasions....
There are 3 fixed types of container boxes categorized by its size, 20 feets, 40 feets & 45 feets which (45') can only put on the 2nd height of a 40' container!
Also you can see the small 20' containers with the small boxes of grey colour...these are the gear boxes...these boxes are owned to the ship ...and the ship cannot sail without them due to that inside them are stored the twistlocks ....mechanisms which secure and keep the containers locked between each other!
2 20' containers loaded same time as one piece
40' containers
45' on the top of a 40' one
gear box
twistlock