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In old routes in European (at least) mountains and in quarries used by cavers for training you can find small expansion bolts called spits or Cheville Autoforeuse. They use just 8 mm thick screws ...
Answer
In old routes in European (at least) mountains and in quarries used by cavers for training you can find small expansion bolts called spits or Cheville Autoforeuse. They use just 8 mm thick screws ...