Ref. wgornick - Help needed: installing the ribber comb with trembling arthritic hands
I have a problem with my hands so I sympathise with your mom - it's lovely that you are trying to help.
This video might help (by The Answer Lady): (copy & paste link)
starting ribbing on the main bed and hanging the cast on comb without removing the wire.wmv https://www.youtube.com/watch?v=izNjyYCiqwc#t=327.688812
I've attached a word doc showing how it was done (for reference after watching the video) - I hope it helps.
I couldn't find a way to add a document to someone else's post - hence this 'new one' - hope you find it OK.
You can use Bulldog clips to hold the comb while you insert the wire.
I agree with jackdigger. A method I sometimes use. Those bulldogs are very handy.