a 'jib' is the section of a crane sometimes referred to as the 'boom', which may or may not be telescopic. If not it may be referred to as the 'stick'.
a 'cropper', sometimes spelt 'crupper', is the section of a horse's harness which passes under the tail and steadies the harness longitudinally. It has a secondary usage in some parts of the US relating to a practice called 'share cropping'
hope this helps
KevUK is, of course, entirely right regarding 45s, sense and any relationship which they may or may not have. As to saddle mountings, my 45 project did at one time feature a suicide clutch, tank shift arrangement using a police shifter lever I acquired as part of a garage clearout. We never did work out how to do it and the shifter has long since been fitted to another bike, where it works very well, but it still has the elaborately engineered cross-bridge and shortened t-bar which have been a great way of fitting a stock-type saddle in the right sort of place, off the original Ariel mountings and using short springs so that it doesn't wobble all over the place.
as a closing item, quite irrelevant but i thought it was rather good fun.. http://www.youtube.com/watch?v=r4wgWqYP9XA