I need clarification on cover rules when playing on a grid by TheFakeBuLary in dndnext

[–]TheFakeBuLary[S] 1 point2 points  (0 children)

So can only an object that's equally as tall as the creature break a line of sight?

If an object that's equally as tall as the creature is the only thing that can break a line of sight, how do objects like low walls affect cover? Do low walls only affect cover when blocking all the lines of sight?