We use 6 x 12" plastic card coloured red, blue, green and yellow.
A split section starts with a normal set of start cards the main route (usually clubman route) is then marked with red cards to the right and blue to the left. When a hard route split arrives the red and blue are laid out with two green cards off to the right or left showing the start of the hard route split. The hard route then continues with green cards on both sides until the routes join again where the last green cards are placed with the red/blue to show the riders they have rejoined the main route again. The same thing is used for the easy route but yellow cards are used instead of green.