A joist is a horizontal member that supports the deck. It runs across each plank so the ECW ABS clip spacers can be screwed in to support / strengthen the fixing the decking boards in place. The span is laid out at equal intervals to support weight on your deck. Note that due to the size of the joists, they are not to be used as a structural component such as on a bridge without adequate support under the joists themselves. Find out more information here.
*2900mm lengths are available on request.