Visible crew/equipment: When all the Darlings walk out of Andy's kitchen with a bag full of Aunt Bee's muffins, the actor's tape mark is visible on the floor, where one of the Darling boys looks down and stands. (00:20:25)
Opie Steps Up in Class - S8-E5
Visible crew/equipment: When Andy walks into the living room at the Hollander's house, the white tape mark is visible on the floor between Andy's and George's feet.
Opie Steps Up in Class - S8-E5
Visible crew/equipment: When Aunt Bee picks Opie up at Billy's house, while Opie tells her all about lunch we can see the reflection of the camera and crew member, on the car's vent window.
Opie Steps Up in Class - S8-E5
Visible crew/equipment: When Aunt Bee drops Opie off at Billy Hollander's house, just as Opie opens the car door the reflections of a crew member and filming equipment are visible on the door's surface.
Visible crew/equipment: After Andy gets the phone call about Sam's victory, when Sam is pushed to give a speech, a few white tape marks are visible on the floor near the fireplace.
Visible crew/equipment: After Emmett talks to to the diner owner about having the bus stop moved to double his diner business, when Emmett walks down the block, the reflection of the moving camera dolly is visible in the store window.
Visible crew/equipment: When Andy, Howard, and Goober walk into Emmett's shop to tell him that Sam's running for head of City Council, the shadow of the boom mic is moving on the wall behind them, at the top of the screen.
The Wedding - S8-E26
Visible crew/equipment: The night of Howard's party, when the doorbell rings and Howard opens the door for Goober, we can see a crew member's head moving in and out of the shot at the right side of the screen.
Visible crew/equipment: After Barney brings the "Fun Girls" to Andy's house, when Aunt Bee walks into the parlor there are now three black tape marks visible on the carpet - and those marks weren't there when Barney and the women walked in.
Visible crew/equipment: At the end, when Barney's talking to all the boys at the courthouse, the camera angle's looking up in Barney's closeups, and the top of the courthouse set is visible right before Barney mentions "intimidation."
Visible crew/equipment: At the courthouse, while Barney and Thelma Lou are trying to stall for time, in the shots facing Andy and Helen when Andy says, "Steaks, chops, macaroni surprise," we can see the shadow of the boom mic moving around at the top, left side of the screen.
The Great Filling Station Robbery - S3-E22
Visible crew/equipment: When Gomer walks into the courthouse with the envelope and Barney takes the photo out, the shadow of the boom pole is moving around on the door and wall to the right.
Visible crew/equipment: While Andy's sitting on his desk going through the mail and Barney's sitting on the side desk, the actors' chalk marks are visible on the floor behind them, in the shots facing both of them.
Visible crew/equipment: When Gloria and Frank drive off at the end, just as the camera zooms in on Andy and Helen, the shadow of the moving boom mic is visible at the top, left side of the screen.
The Education of Ernest T. Bass - S5-E4
Visible crew/equipment: When Ernest T. runs across the street to help Helen with her groceries she rushes away from him and heads up the block to Andy, and as Andy and Helen walk toward the courthouse the shadow of the boom mic passes across the white pillar in front of the door.
Visible crew/equipment: When Barney walks into the bank dressed as a woman, we can see the two curved chalk actor's marks on the floor behind the teller.
Deputy Otis - S2-E31
Visible crew/equipment: After Otis admits to Andy the reason why his brother thinks that he works at the courthouse Otis walks back to the cell, but when Andy calls him back and gets up, just as Andy walks around the desk we can briefly see two actor's marks where they will stand momentarily.
Visible crew/equipment: When Barney and Thelma Lou leave Mary's house the curved chalk actor's mark is visible on the floor by the door. Then Barney shows up again with his drum, and we can see a chalk T-mark on the floor. That same T-mark is also there in a later scene, when Barney barges in with the letter he found behind the file cabinet.
Visible crew/equipment: Right after Mrs. Williamson leaves the barbershop upset about the carp killing, when the mayor says that they have more important things to talk about - which is the celebration, we can see the curved chalk actor's marks where Williamson had been standing.
Visible crew/equipment: When Barney's reading the Sunday comic strip Andy comes in to close the jail in the courthouse, and when Otis walks out of his cell we can see the actor's chalk mark on the floor where he stands.
Answer: Those "boxes" are valences that used to be very common, before air conditioning. They allow for windows to be open during rain storms. They permit air circulation, without letting the rain in.