Good way to remember the difference between p, q, d and b

[Jogonjill]

My son is loving learning his letters, and is starting to put them together to make sounds. However, he is finding it hard to recognise these four letters, and often substitutes one for another. I imagine that if I keep gently correcting him, he will come to recognise them better over time, but is there a helpful teaching mnemonic that anyone knows of to reinforce the difference? I don't want to confuse him or put any pressure on him, just continue to learn in a mainly incidental way, so something story or drawing based would be great.

b & d use a picture of a bed with the upstrokes being the head and foot boards. there will be something on-line as a teaching resource, but cannot look for it now.
Also if you clench your fists with the thumbs pointing upwards, then put your fists together that can look a bit like a bed and can be used for checking and reinforcing the picture.

bed is a good one for b and d as if you draw a bed (without legs!) and then put a sort of circle in the corners it looks like the b at one end and the d at the other, iyswim!

cross posts!

Thanks both, I shall try that now!