Other mistake: In the bookie's apartment, on the table with all the telephones, there's a can of scouring cleanser which has the "a" and "x" covered, so all we see is the "ja" on the can, in order to hide its brand name, which is Ajax.
Other mistake: After the explosion occurs in Rampart's basement, when Engines 236 and 73 roll up on scene, we can see the engine companies' numbers are covered up atop their cabs, presumably to conceal the engine companies' real numbers.
Other mistake: Over the phone the bookie tells Sidney, "I'm having them pains again. I don't feel so good. Would you call some...," then collapses onto the floor. Then Station 51 is dispatched to "Possible heart attack," and the address is given, along with the apartment number 23. After 51 breaks into the bookie's apartment, soon one of the phones ring and Captain Stanley says, "Let me get this straight. Your name's Sidney, and you phoned in the heart attack, right? Now we're getting somewhere. How come you didn't have the address? What's your last name Sidney?" However, 51 was dispatched to the proper address and even the apartment number. Nobody else knew of the heart attack, and the victim did not phone it in.
Answer: It is standard practice to wet down driveways so that they stand out in a long shot.
stiiggy