Method of assembling a dumper vessel of a box type dumper truck, which makes sure a front bollard profile, side panel profiles and a back bollard profile that constitutes the dumper vessel of the box type dumper truck are engaged so that they complement one another geometrically and combined with a welding method, wherein the method includes: • Making sure that the front bollard profile and a side panel profile are combined, wherein: ∘ a front bollard profile side panel protrusion (4.2) is positioned in a side panel profile front cove (5.2), ∘ a side panel profile front protrusion (5.1) is positioned in a front bollard profile side panel cove (4.3), ∘ a side panel profile front welding bevel (5.6) is welded together with a front bollard profile welding bevel (4.1); • Making sure that a side panel profile is combined with another side panel profile, wherein: ∘ a side panel profile front protrusion (5.1) is positioned in a side panel profile back cove (5.4), ∘ a side panel profile back protrusion (5.3) is positioned in a side panel profile front cove (5.2), ∘ a side panel profile front welding bevel (5.6) is welded together with a side panel profile back welding bevel (5.5); • Making sure that a side panel profile and the back bollard profile are combined; ∘ a side panel profile back protrusion (5.3) is positioned in a back bollard profile front cove (6.2), ∘ a back bollard profile front protrusion (6.1) is positioned in a side panel profile back cove (5.4), ∘ a back bollard profile welding bevel (6.3) which is welded together with a side panel profile back welding bevel (5.5). • Making sure that the front bollard profile and a side panel profile are combined, wherein: ∘ a front bollard profile side panel protrusion (4.2) is positioned in a side panel profile front cove (5.2), ∘ a side panel profile front protrusion (5.1) is positioned in a front bollard profile side panel cove (4.3), ∘ a side panel profile front welding bevel (5.6) is welded together with a front bollard profile welding bevel (4.1); ∘ a front bollard profile side panel protrusion (4.2) is positioned in a side panel profile front cove (5.2), ∘ a side panel profile front protrusion (5.1) is positioned in a front bollard profile side panel cove (4.3), ∘ a side panel profile front welding bevel (5.6) is welded together with a front bollard profile welding bevel (4.1); • Making sure that a side panel profile is combined with another side panel profile, wherein: ∘ a side panel profile front protrusion (5.1) is positioned in a side panel profile back cove (5.4), ∘ a side panel profile back protrusion (5.3) is positioned in a side panel profile front cove (5.2), ∘ a side panel profile front welding bevel (5.6) is welded together with a side panel profile back welding bevel (5.5); ∘ a side panel profile front protrusion (5.1) is positioned in a side panel profile back cove (5.4), ∘ a side panel profile back protrusion (5.3) is positioned in a side panel profile front cove (5.2), ∘ a side panel profile front welding bevel (5.6) is welded together with a side panel profile back welding bevel (5.5); • Making sure that a side panel profile and the back bollard profile are combined; ∘ a side panel profile back protrusion (5.3) is positioned in a back bollard profile front cove (6.2), ∘ a back bollard profile front protrusion (6.1) is positioned in a side panel profile back cove (5.4), ∘ a back bollard profile welding bevel (6.3) which is welded together with a side panel profile back welding bevel (5.5). ∘ a side panel profile back protrusion (5.3) is positioned in a back bollard profile front cove (6.2), ∘ a back bollard profile front protrusion (6.1) is positioned in a side panel profile back cove (5.4), ∘ a back bollard profile welding bevel (6.3) which is welded together with a side panel profile back welding bevel (5.5).