No, as in these variants, the corners act as if there was a piece of the currently moving player sat upon them, so you can capture a piece by surrounding it between one of your own pieces and a corner square. There is evidence that, on some boards (the alea evangelii 19x19 board), there were fixed men attached to the corner squares. In others (like the Ballinderry 7x7 board) the corners had more subtle markings on them.