a chain is no stronger than its weakest link

a chain is no stronger than its weakest link

If one part of something is weak, it jeopardizes the integrity, quality, or effectiveness of the whole. I need to make sure that everyone on our debate team is well-prepared, since a chain is no stronger than its weakest link. A chain is no stronger than its weakest link, and our security will not be effective if any of the checkpoints are not functioning.
See also: chain, link, strong, weak