Related Clues:
- Bound to get over them underground
- Leaps over
- They may be hard to crack
- Places for rings, maybe
- They may be cracked using stethoscopes
- Bounds within which wines are stored
- Jewel cases?
- They may be blown or cracked
- Vaults for valuables
- They're still often dialed
- Hiding places in walls
- Money holders
- What walls might hide
- Cracksman's targets
- 'A paper currency is employed, when there is no bullion in the --' (Emerson, Nature)