What is the opposite of a metaphorical barrier?

I am trying to find a noun that describes a person that enables others to be more productive. The opposite of that is a roadblock or barrier.

My first thought was a sail, since the addition of another sail in the correct place allows a ship to reach its destination faster. But this strikes as too obscure.

Is there a shared metaphor/simile that would capture this idea and satisfies these conditions

• noun that can be applied to a person (Bill is a ... )
• not obscure
• helps others achieve their goals better (rather than his own goals)

Solution 1:

More literal

As opposed to a hindrance:

• Bill is a facilitator:

[Merriam-Webster]
: someone or something that facilitates something
especially : someone who helps to bring about an outcome (such as learning, productivity, or communication) by providing indirect or unobtrusive assistance, guidance, or supervision
// the workshop's facilitator kept discussion flowing smoothly

More metaphorical

As opposed to a roadblock:

• Bill is a passageway:

[Merriam-Webster]
: a way that allows passage

Depending on the required nuance, gateway could also be used.