Port Elizabeth - England captain Joe Root produced a Test-best bowling performance to send South Africa hurtling towards a humiliating defeat on the fourth day of the third Test at St George's Park on Sunday.
England dominated the day despite a second lengthy rain break in two days.
Wood used his extreme pace to send Dean Elgar's off stump flying out of the ground before he had Zubayr Hamza feeling for a ball outside his leg stump to present a catch to wicketkeeper Jos Buttler.
Root took three more wickets after the interval.
In overcast conditions at the start of play, Broad and Sam Curran achieved some swing with a ball which was almost new, but they were aided by some poor shots by the South African batsmen.
De Kock had not added to his overnight score of 63.