Place the left rope over the center rope. Then place the right rope over the new center rope. Repeat until you've reached the end of the ropes. For a Rosh Hashana round challah, make your ropes long and skinny. After braiding, coil the braided dough up like a snake, starting in the middle and working out.
Some people skip the braiding and just coil.
Seal the end with a moistened finger. Wipe the dough with the reserved egg, using a brush or paper towel. Cover it with a tea towel and leave it to rise for 1 hour. If you like your challah especially shiny, after dough has risen, gently wipe it with some more reserved egg, using a brush or a paper towel. For a sweet Rosh Hashana challah, dribble some honey on too .