how to stop a backfist?

I know this is a newbie question… but my sifu has never really gone over any techniques about dealing with a horizontal backfist.

The reason I ask is because I was doing some light sparing with my bro, and those were pretty much the only thing I couldn’t “block”, not effectively any way (tried combining other techniques to stop them, but it didn’t work very well…)

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Depends how “flicky” the backfist is. If it’s a flicking backfist, a straight punch w/ a forward step can usually do the job.

It’s a different story if it’s a directed backfist w/ full body motion (e.g., a spinning backfist).

Perhaps you can better describe the situation?