I am happy to be the first reviewer of Keith Heinritz Catering. This is the place to come for incredible fish sandwiches on the east side of Pittsburgh. Don't be alarmed by the "hole in the wall" appearance from the outside because the inside is the same (ha ha). This is a pretty clean place for the high volume of activity going on here. If you order a large fish sandwich - it is enough to feed 2 people (but you may want to get an extra bun or 2). The krinkle cut fries and clam chowder soup are also very good.
What makes the fish so good? Very good light breading but most importantly - extremely fresh tasting big chunks of perfectly fried fish. The big hunks of fish tend to fall apart when you eat it. Not greasy like some fish fries. No sign of a bad or old taste to the oil and fried stuff despite the long line and high volume. Perfect and yummy. They have about 7 or 8 workers swarming in the little kitchen and they seem to be serving it up fresh with minimal wait.
A few more important notes - CASH ONLY. If you want to go on a Friday in Lent, you should consider ordering and picking up before 5:00pm to avoid the longer lines. There are some tables in here but most people take out. These folks are the experts - much better fried fish than that church basement down the road (please don't tell the priest or pastor that I said that). Give this place a try.