Create horizontal parts
When creating horizontal parts, such as beams, always pick points in the same direction. For example, pick positions from left to right, and from bottom to top (in positive x, y directions). This ensures that Tekla Structures places and dimensions the parts in the same way in drawings, and that part marks automatically appear at the same part end.
To ensure that beam rotation is correct in drawings, set part Rotation to Top in the part properties.