Tables :: How To Hold Matrix Data In A Table

In my DB there is a set of company-running rules that are addressed to different groups within the company, like drivers, bookkeeping, warehouse, electricians etc. Both groups and workers scope and number might change from time to time. I need to make a table that holds which worker belongs to which of these groups (one worker to one or more groups). The easiest way of setting this for the user would be kind of a matrix-look form where lines would hold the name of workers, columns would hold the groups and at the cross points there would be check boxes to set or unset membership. However I can't find the way in what table sturcture this could be utilized.