Barkbone Strapping

Instant - Destroy this: Roll a 6 sided die. Gain

equal to half the number rolled, rounded down.

Battleworn

Rulings

From the Welcome to Rathe release notes

If the number rolled is 1, no resources would be gained.
You may use Barkbone Strapping’s activated ability even when there is no cost to be paidBarkbone Strapping’’s activated ability is an instant. You may activate it any time you have priority, including during an opponent’s turn, and during the reaction window of either player’s turn.

Keyword notes

Battleworn - Equipment that wear down after each time they are used to defend. If you defend with a card with Battleworn, put a -1{d} counter on it when the combat chain closes.

When you defend with a card it remains on the combat chain until the chain closes, therefore you cannot defend with an equipment multiple times on the same combat chain.
A -1 counter stays on the card until the card is destroyed or the game ends.
If the defense of a card that is defending is below zero, its defense value is considered to be zero.
When this card is destroyed, it is sent to your graveyard. (Not when it has 0)
When this card is destroyed, it is sent to your graveyard.
If the defense of a card that is defending is below zero, calculate as if its defense is zero.