to fail to do something that you should do.

The armed forces will take over if the local authorities fall down on the job.

• put your life in hands
• put your life in someone's hands
• put your life on the line
• put your mind to it
• put your money on someone
• put your money on something
• put your money where mouth is
• put your money where your mouth is
• put your neck on the block
• put your neck on the line
• put your oar in
• put your own house in order
• put yourself in place
• put yourself in someone's place
• put yourself through
• put yourself through something
• put your shirt on
• put your shirt on something
• put your shoulder to the wheel
• put your thinking cap on
• put your two cents in
• put your two cents worth in
• puzzle out
• puzzle out something
• puzzle over