Joist braces were made to work in tight spaces where a full brace and bit wouldn't fit.
Various models were made, a common version was the Skinner joist brace.
This model has no identifying marks
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1) Modern features, ratcheting mechanism.
Early features, bit holder, screw out back support.
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2) Note: screw out back support
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3) Early bit holder
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4) back support wound out.
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5) back support wound in
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6) Bit holder and thumb screw. Ratchet mechanism
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7) Ratchet mechanism and back support.
8) Handle