I would describe it as a trip charge, but in the details I would write:
Missed appointment. All [your company name here] personnel and equipment were on site with tools unloaded from the van, ready to work. Product to be provided by client was not on site. Time: 3 men x 2 hours = 6 labor hours at our normal rate (or whatever it was).
At that point you can indicate a good-will discount down to what you really wanted to charge.
I'd add a note on another line: In future, this kind of charge can be avoided by telephoning us 24 hours in advance of the agreed-upon time.
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
