GD and T - How to draft a keyway?

I need to make a blueprint with a 4mm keyway. What would a proper GD and T callout look like? Can someone post a picture of it please?

1 Answer

I have attached a drawing with the proper way to dimension a keyway in a hub part. The main reason it has been dimensioned this way is because this gives the workman definate fixed points for setting up hub to have key way broached / machined and to check finished keyway.