What's the difference between a "nook" and a "cranny"?

In the OED’s definitions, nook seems to have the meaning of some kind of corner, whereas a cranny is some kind of opening or crack. Together they cover a range of possible places in which a thorough search might be conducted. I think either on its own would be rare in current English.

1)A "nook" is a corner or a small, partially enclosed area of a larger room. A "cranny" is a crack or a crevice.

2)A nook is a sheltered and secluded place.

3)A nook is a recess esp. one offering seclusion or security. A cranny is a small narrow space or opening.

4)A nook is a small corner of a house, or a secluded spot. A cranny is a crack or hole in something

5)A nooks are high, crannys are low. A cranny is a a long narrow depression in a surface.

6)A nook is in. A cranny is out.

The phrase 'every little nook and cranny' means every part or aspect of something.