keep hand in
keep one's hand in (something)
Fig. to remain involved in something, perhaps only a token involvement. I want to keep my hand in things even after I retire. I always have to keep my hand in so I will feel a part of things.
keep your hand in (something)
to continue to be involved in something Rick turned the business over to his son, but he comes in Fridays to keep his hand in.
keep your hand in
to practise a skill often enough so that you do not lose the skill I do a bit of teaching now and then just to keep my hand in.