Extension (T11)

"The panel with arrows pointing in two directions, placed horizontally or vertically, means that the indication applies to both sides of the sign. The panel with the arrow pointing down means that the indication ends there. The panel with a right or left-pointing arrow means that the indication applies in the direction to which it points. If the panel is used under an E19 sign, parking, the black symbol is on a white background with no border. The panels can also be used independently to demarcate parking spaces in an area, if there is a sign at the entrance to the area stating that parking is permitted."

Types of arrows

Two-way arrows: The road sign applies to the front and back of the sign
Downward arrow: Road sign ends here
Right or left arrow: Road sign is valid to the right and left

Extension (T11-1) left arrow

Extension (T11-4) left arrow
No Arrow: If the sign has no arrow it means this sign is valid from this point forward. This is (similar to an up arrow). Thus it makes it unnessesary to add this type of arrow , else every road sign requires an up arrow