The valvular leaflet
The chordae tendinae function like the chords on a parachute that attach to the chute mechanism. Without the chords to provide tension and anchor the chute against the air, the chute would fail and the parachute would not function.
Likewise the chordae support the valve
leaflets and allow them to line up and formn a functional seal. Abnormal chordae can cause a valve to leak or open ineffectively.