The drawing below is from Gustave Eiffel's book describing the tower that bears his name. There are 53 of them in total.
XII bis. Panels 16 to 18
The panels 16 to 18 are those of the junction of the 4 batteries in a single pylon, they must be calculated independently of the rest, this is the reason for the presence of this board. In addition to the cutting planes, there are many technical assembly details, but also the description of the 2nd floor staircase and the way it is attached to the rafters.
See also: