Bunging your holes up

My dear old mum was a funny loving person, talking to everyone and just  made life brilliant.  We lived in a little village and close to a set of local shops.  When we were little she regularly visited the local shops for odd bits of shopping.  One day she met this man in one of the shops, while buying ground coffee, that proceeded to have a discussion with her about how not to get your holes bunged up on the coffee percolator.  He told her that she had to have the percolator on number 5.  He was a posh man with a big black beard and gave her strict instructions what to do.  She thanked him and said she would try that and let him know.  On her next visit to the shops she saw this man across the road and ran after him tapped him on the shoulder and said you were right number 5 didn't bung my holes up. The bearded man looked at her and said, in a Scottish accent, I beg your pardon. He was the wrong man and he had no sense of humor either! She bumbled along trying to explain to him what had happened without a glimmer or a smile from him.  In the end she said to him oh well you probably don't have any holes to bung so you wouldn't understand and promptly walked off!