Related Clues:

• Blocks (up)
• Electricity generators
• Blockades, of a sort
• Beavers' constructs
• Beavers build them
• They may cause course reductions?
• Beavers' projects
• Beaver-built barriers
• River regulators
• Creek blockers
• Lake creators
• Spots for drawbridges
• Beaver-built blockages
• Beaver barriers
• Some zoo barriers