Was recently clipping some electrical cables to a bare brick-wall
prior to it being plaster-boarded.

However, if I hammered the clips into the mortar, they just fell out
again - the wall is ~70 years old.
And try as I might, I could not get them to hammer into the brick.

What's the usual way of attaching these to a brick wall?
Hammer into brick or mortar?

Thanks,
Mark.