John
I can only quote from David J Smith's book.
"In the GWR Rule Book of 1923 reference was made to 'safety points', whilst in the 1933 Rule Book, and the 1945 reprint, the term'trap points' was used, meaning in each case switches intended to divert or derail any vehicle moving without authorisation from a siding or a loop towards a running line, but among permanent way staff they were invariably known as catch points, and were described as such in documents and drawings. Only with the advent of nationalisation, under the pervasive LMS influence, was the rule book appelation ultimately adopted."
So, on the GWR, those who did things called them catch points and the blunties in admin called them trap points. All the GWR drawings in the chapter are labeled 'Catch Point' by the original draughtsman. There is a section on runaway catch points described by Smith and these were just long lead single tongue catch points spring loaded open. There are complicated rules describing their position in relation to the Home signal.
See what I mean about the dry style? A 73 word sentence!
Simon
PS, I suspect that your example in the photograph is the way to do it. If only I could find a GW example!