On the fence and Weak-kneed

On the fence adjective - Characterized by indecision.

Weak-kneed and on the fence are semantically related In some cases you can use "Weak-kneed" instead an adjective phrase "On the fence".

Weak-kneed adjective - Lacking strength of will or character.

On the fence and weak-kneed are semantically related in uncertain topic. Sometimes you can use "On the fence" instead an adjective phrase "Weak-kneed", if it concerns topics such as indecisive.