skeleton key 
noun
A key designed to fit many locks by having the interior of the bit hollowed.He slid a skeleton key into the lock, and eased the door open....
- Officer Humphrey put the skeleton key into the lock in order to get the door open.
- Taking a sharp breath in, she opened the package and found a heart shaped locket key chain with a skeleton key.
- roundtail
- round text
- round the bend
- round-the-corner
- round-the-houses
- round-the-table
- round the twist
- round the wicket
- round-the-world
- round-the-worlder
- round-the-year
- round tilth
- round timber
- round-toed
- round tool
- round top
- round towel
- round tower
- round-towner
- round trade
- round trip
- round-tripper
- round-tripping
- round turn
- round turnip