Core: The marker board: who, when, how big?

WHO: the board duty applies to the trailer, not the passenger car. So on a car with protruding load a marker board is not required (Book p.229). WHEN (trailer): required if the load protrudes more than 10 cm at a side, or more than 1 m at the rear. HOW BIG: the legal minimum is a square board of 0.42 x 0.42 m. The often-quoted '50 x 50 cm' is a common commercial size, not the legal floor. WHAT IT LOOKS LIKE: red-white diagonally striped, retroreflective, with stripes 7 to 10 cm wide. Red-white, not blue-white. AT NIGHT: at least one white light at the front (for oncoming traffic) and one red light at the rear (for following traffic) — just like ordinary vehicle lighting.