A * * * has 2 wooden cases +4 iron boxes = 1 iron box +4 iron boxes =5 iron boxes =5 copies.

20 glass balls are divided into 5 parts, each part has 4 glass balls.

One is packed in an iron box, so there are four glass balls.

Two wooden cases contain 1 serving, so one wooden case can only contain half, that is, two glass balls.

So the answer is that two glass balls are put in a wooden box and four glass balls are put in an iron box.