Shield slam: "Free" bull rush is mandatory or optional?

[Ainslan]

Title pretty much sums it up. Does taking the Shield Slam feat means that from then on, each and every time I hit a foe with a Shield Bash I gotta check against it CMD to see if it is pushed back, or may I instead elect not to have the foe be bull rushed by my shield on a particular attack?

The usage of the word "free" in the feat description confuses me, as it does not seem to be either clearly mandatory or clearly optionnal.

[Vaellen]

Ainslan wrote:

Title pretty much sums it up. Does taking the Shield Slam feat means that from then on, each and every time I hit a foe with a Shield Bash I gotta check against it CMD to see if it is pushed back, or may I instead elect not to have the foe be bull rushed by my shield on a particular attack?

The usage of the word "free" in the feat description confuses me, as it does not seem to be either clearly mandatory or clearly optionnal.

It's optional.

[Asgetrion]

Vaellen wrote:

Ainslan wrote:

Title pretty much sums it up. Does taking the Shield Slam feat means that from then on, each and every time I hit a foe with a Shield Bash I gotta check against it CMD to see if it is pushed back, or may I instead elect not to have the foe be bull rushed by my shield on a particular attack?

The usage of the word "free" in the feat description confuses me, as it does not seem to be either clearly mandatory or clearly optionnal.

It's optional.

+1.

[Elven_Blades]

Optional

The use of the word "free" means that you do not need to spend a (move/standard/full round) action to Bull Rush your opponent.

[BigNorseWolf]

Optional. If a rules lawyer needs confirmation

grant you the ability to take actions otherwise prohibited to you.

You are able to take the action the feat lets you do, not required to.