Alternative form of knob-and-tube

Of or pertaining to a type of electrical wiring consisting of insulated conductive copper wire affixed by porcelain hardware and protected in vulnerable areas by insulated cloth sleeving. Widely used in North America during the late 19th and early 20th centuries.

plural of known universe

Two parts of an organization are unaware of each other's activities.

Don't criticise something before having experienced it.

Alternative form of know what is what

(idiomatic) To be experienced or well-informed. / (idiomatic) To be astute, perceptive enough to observe a situation that is not what it seems and recognize its true nature.

Alternative form of know inside and out

(transitive, simile) To have an extensive and penetrating understanding of (something or someone).

(also philosophy) Be aware of your own strengths and limitations.