Mystery Solved: Why Semi-Automatic Washing Machines Have Ridges

• Semi-automatic washing machines feature ridges on their wash tub walls, often mistaken for design.
• These ridges serve as a built-in washboard, allowing users to hand-scrub stubborn stains like shirt collars.
• A viral video recently revealed this hidden function, surprising many long-time users.
• The design is inspired by traditional hand-washing methods, where clothes were scrubbed on ridged boards.
• Many brands like LG, Samsung, and Onida incorporate this feature, sometimes with a dedicated 'scrub basin'.