The only time I use a crook is when I'm posing around judging
For catching sheep in pens, I would crowd them into the corner then take hold of the one I want (not by its wool, ever). If the pen is too big to do that, so you find yourself running round it chasing the sheep, you need to close down the pen to make it smaller. For catching them out in the open, I don't. Occasionally Mr F has to catch a new born Heb lamb to do its navel, tag, sex etc (Heb lambs are up and running like the clappers within a few minutes so if you miss them being born it can be a problem, and if they need castrating when I few days old, well, it's near impossible to catch the little blighters, but a crook wouldn't help) - so, he has perfected a sort of rugby tackle, but I can't do that. Can't run either.