No roof access

Signs that may appears in the stair ways. This means you cannot get to the top of building through normal ways.
TRY TO CLIMB UP THE WALLS.

J: No roof access in this stairs. Can't we find a way to the top and shoot some fireworks?
B: Climb up the wall then.
J: Never.

slide rule

a tool made up with two or three rules that are skewly and weirdly marked. Allow you to slide back and forth to get some calculations done.

NOT FOR MEASUREMENT AND PUNISHING PEOPLE WHO ARE MISBEHAVED.

Man1: OMG, what's wrong with ruler, it has too many strange marks and are almost skewed. How could someone measure stuff out of that?
Man2: Bro this is a slide rule.

duck typing

Programming stuff.
If that thing can be throw into your oven and taste like a roast duck or whatever, and it lucks has wings and legs and ankles, that is a duck.
duck typing focus on the acts or the method but don't care what this thing actually is.

Jack: look at that bird, it can swim, it has two wings, it must be a DUCK.
Ben: That is a goose. Nerd. Stop duck typing.