Uneven walls and floors
Cabinets should be level even when the building is not. Adjustment at legs, rails, fillers and finishing panels is planned around the actual room rather than copying an uneven surface.
Corners and door clearances
Corner geometry affects handles, drawers, appliance doors and adjacent fronts. A few millimetres of clearance can decide whether two components can open without conflict.
Services and appliance spaces
Sockets, plumbing, waste pipes and ventilation routes can affect cabinet positions and access panels. Furniture should not be used to conceal a service problem that requires the appropriate trade.
Solve the constraint before finishing
It is usually easier to correct spacing and alignment before worktops, plinths, fillers and handles are finalised. The sequence matters because later components lock earlier decisions in place.