Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4740948.
Carabiner with compliant mechanism.
This carabiner has a spring-loaded gate, designed as a compliant mechanism. Hinge and spring are printed in place, so no assembly is needed. Therefore the whole model is just one continuous volume.
The carabiner is not designed to carry huge loads, rather it is a demonstrator for this kind of mechanisms. The strength of the spring could be adjusted by varying its thickness. The gap of the hinge (0.3 mm) requires a well calibrated extruder unit, otherwise there may not be enough clearance for movement.
PETG is recommended as material due to lower Young's modulus. PLA should also work, but might be not flexible enough.
Geometry was created using Rhino.