The surface of the junction is typically marked with a yellow criss-cross grid of diagonal painted lines (or only two lines crossing each other in the box), and vehicles may not enter the area so marked unless their exit from the junction is clear, or they are intending to turn and. The surface of the junction is typically marked with a yellow criss-cross grid of diagonal painted lines (or only two lines crossing each other in the box), and vehicles may not enter the area so marked unless their exit from the junction is clear, or they are intending to turn and. Box junction markings are easily identifiable due to their distinctive yellow criss-cross grid pattern. The lines are painted in such a way that they form a series of small diamonds within a larger square or rectangle. The markings are usually bright yellow to ensure they are highly visible to. Road markings are the instructions painted directly on the road surface. For the theory test, and for safe driving, you need to know what each marking means and the rules about crossing or entering them.