I can usually shade something but I'm not confident it's the right area.
Accepted answer
Deadweight loss is the value of mutually beneficial trades that no longer happen.
It appears whenever quantity is pushed away from the competitive equilibrium — a tax, price floor, price ceiling, quota, monopoly output. Those units were worth more to buyers (demand curve) than they cost to produce (supply curve), so removing them destroys surplus nobody captures.
To locate it: mark the efficient quantity (where supply meets demand) and the actual quantity. The triangle sits **between the supply and demand curves, spanning those two quantities**, with its point at the efficient equilibrium. If you can state which trades stopped happening, you've almost certainly shaded correctly.