Calculate the total horizontal length of the structure shown in the elevation. The horizontal segments measure 1800 mm, 1800 mm, and 2550 mm.

The drawing indicates three horizontal segments with the following lengths:

• $1800\, \text{mm}$
• $1800\, \text{mm}$
• $2550\, \text{mm}$

$$\text{Total horizontal length} = 1800\, \text{mm} + 1800\, \text{mm} + 2550\, \text{mm}$$ $$\text{Total horizontal length} = 3600\, \text{mm} + 2550\, \text{mm}$$ $$\text{Total horizontal length} = 6150\, \text{mm}$$

The total horizontal length of the structure shown in the elevation is $\boxed{\text{6150 mm}}$.