Left-hand means on or towards the side where the heart lies. The left-hand lane.
The hyphenated form is the one that pairs with side, corner or lane. Left-handed people are about one in ten and every tool assumes they are not.
1adjectiveleft-handOn or towards the side where the heart lies, in the hyphenated form that pairs with side, corner, or lane.
“The handle is on the left-hand side of the door.”
left-hand is a quality.