Artikel 18

If the tonnage deck is interrupted, within the meaning of Article 10, third paragraph, for a portion of its length (see Figure 10), the tonnage length should be measured on an imaginary line in continuation of the original deck.
In the case shown in Figure 10 it may be advisable to transfer the extreme points of the tonnage length to the top of the superstructures and to measure the length over the latter. As the distance from the under side of the deck which covers the superstructure to the line of continuation is equal to the height of the superstructure, the extreme points of the tonnage length are found by setting down this height. It is necessary, of course, to take into account the frames, the ceiling (if fitted) and the round of beam, where such exists.