The rules of the competition (Rule 2.c.1) prohibit players playing for more than one team or one age group.
The Covid situation makes things more difficult and the RFU guidance is that efforts should be made to get players playing.
Cheshire RFU has decided to amend this rule for teams/clubs who have issues with player availability due to Covid isolation requirements.
Players playing for more than one team within one Club will be allowed as long as the requirements of Regulation 15 are met in terms of playing up or down and as long as the opponents have been informed and have given their agreement.
This will not form a precedent for future competitions, and can only be done on a match by match basis with the explicit approval of the M&J secretary (i.e. you have to ask again for the next game).