The Bolton Building is billed as 12 floors tall for the climb, but the building shown is only 10 floors tall. The International Savings & Exchange Bank Building in LA was actually used.
The Girl is wearing a ring on her right ring finger while she's reading the letter. The ring disappears on closeup.
When Harold returns to get The Girl's purse from the General Manager's office, he overhears the GM talking about attracting people to the store. When he is talking to the other man, the purse is on the camera side of the desk, but when Harold comes in, it has moved to the other side of the desk.
The employee number on Harold Lloyd's pay envelope is 205, but on the complaint slip he's handed, it's 170.
On the lower part of climbing the building, Blackstone can be seen down the street (to Harold Lloyd's right), but after the girl notices Harold climbing, there is a different view down the street, and after The Boy passes the clock, there is a third view, all from the same perspective.
The Boy purchases a chain from a stereotypically-portrayed Jewish jeweler. He buys it on a Saturday, when it would be expected that the jeweler would be closed.
When Harold Lloyd has a mouse up his trouser leg and falls to be hanging on the ledge by his fingertips, he has shifted to a stunt double;: Lloyd parts his hair on the right side, but the stunt double has his part on the left.
The prop anemometer at the top of the building is composed of spheres, instead of the half-spheres of a true anemometer.
A line can be seen attached to the man's toupee. This is what causes it to fly off his head, not the mouse that lands on him.
When The Boy (Harold Lloyd) is climbing the upper part of the building (by the clock), the background collection of buildings is different from those when he is on the lower part.
When Harold Lloyd swings on a rope to kiss The Girl on the roof, it's played back in reverse; he's actually hugging her, then jumping.
When The Boy receives his paycheck from the store employee and opens it, his pay stub has the name "Harold Lloyd" on it. While this is the name of the actor, it is not supposed to be the name of the character. The character, as in most of his films, is known only as The Boy. This is the only incident in Harold Lloyd's film career in which he plays a character using his true name. The scene was edited in without Lloyd's knowledge, and he didn't become aware of it until the movie was complete.
A sign in the jeweler's window says that the lavalier chains are "Half Off Today Only," but Harold Lloyd pays the price on the tag attached to the tray: $15.50. The correct amount should have been $7.75, as the jeweler would not have made a separate price tag for a one-day sale.