Edwards & Co OSCAR MX HMV501 Instruction Manual page 21

TIGHTENING & LOOSENING STRAPS
To tighten and loosen the harness, pull the straps through the toggle
on the shoulder strap and/or the crotch strap as pictured.
The straps should be firm but not too tight around your child. You
should be able to fit two fingers in between the harness and your
child.
WARNING!
connected when not fitted to a child in the stroller. The
harness can form loops which may be a strangulation
hazard.
Never leave a harness