A knobstacle is a person who maliciously obstructs or otherwise prevents you from the reasonable transaction of legitimate business.
"I asked the customer service girl to transfer me to her supervisor, right? Huge mistake! Her supervisor ended up being a ginormous knobstacle who gleefully refused to refund my over-limit charge even though he could see that the merchant had refunded me $29.95 from the accidental overcharge that put me $4.95 over-limit in the first place!"
someone who becomes a knob by getting in your way
Naomi's walking to the Cafe, and a student gets in her way. She thinks to herself "What a Knobstacle?"