When I do this correctly, the students don't accidentally see something which may make immature students giggle.
I have had multiple colleagues tell me that this technique worked for them and saved them from repeating an embarassing classroom event.
The instructor will draw the bonding MO of dihydrogen without accidentally causing laughter in the class or self embarassment.
chalkboard or whiteboard
ability to adjust quickly just in case
I have come close to accidentally drawing the incorrect version of this diagram and I am able to stop myself quickly as illustrated in the instructions.