This operates via a pull-string, tied to the bottom of the inner-cylinder. Everything else is mounted on the wall. Assembly is shown in the pictures. All screw holes are 4.5mm diameter.

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Travel distance of the latch is ~14mm, but this can be increased by scaling the Z of the "lower slide" and "inner cylinder" pieces.

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At current scales, this should require a spring with 3/8" diameter and 1.5 to 2" length.