Those outside can see in and those inside can see out and they have one very important rule - People who live in glass houses should not throw stones

The riverbed had gray, black, and white stones.

We built the wall with stones.

People who live in glass houses should not throw stones.

People in glass houses shouldn't throw stones.

The meaning of this is that people with problems shouldn't criticize others.

those people who are themselves suffering from shortcomings should not find flaws in others