If you do not use plywood, foundation and joist must be 120mm or more. Otherwise basis (horizontal member) side screw will penetrate as it is 115mm. Make sure to use dedicated screw which is included. Square bit(#3) are sold separately.
Used to connect pillar and horizontal beam
Testing Center for Construction Materials
HP12-KT004 / HP12-KT007 (stock) performance test house plus confirmatory test