OK I am new to this tool and just started to use it, I spent some time trying to figure out if I was doing something wrong and then discovered that this feature is not an option. I wanted to have four or five check box's for items to be selected but allowing for more than one check box to be clicked.
I have now moved to a select list field type which does support multiple selections. So I can continue.
But I am left wondering if this could be provided. When the number of items is quite small the form is easier to complete with multiple check boxes. It seems that j fields do allow for multiple check boxes so it should be possible.