Dolly Shepherd references the trapeze triangle bar in her book “When the Chute Went Up”. The parachute lines were attached to the trapeze triangle bar with a sling between the corners of the lower apexes. The parachutist would sit on the sling (swing seat) and hang on to the trapeze triangle bar (base bar). There was also an optional belt with a hook attachment the parachutist could safety themselves to the base bar.
This was over one-hundred and ten years ago.
I highly recommend reading:
"When the Chute Went Up" by Dolly Shepherd
Excerpt:
Hazards of the Air
From time to time a member our team might ‘disappear’. Nothing would be said. He or she would just not be seen at any more shows, and if questioned, Captain Gaudron would merely say that the aeronaut in question had ‘left the team’. They had left, sure enough!
So Maud Brooks had ‘disappeared’, and Viola Kavanah, Devil-may-care Captain Smith and handsome, dashing Captain Fleet – They “disappeared’ too.
We learnt not to question these departures, for death was a subject on which we did not dwell. We might read of such an event in a newspaper, but if we did, our reaction was that of most people who flirt with danger: it might happen to them but never to me.