The tried and tested running leger is the perfect rig for both uptide and downtide fishing for thornbacks.
Start with a boom sliding on either the mainline or leader, followed by a bead that acts as a buffer, and then a small, strong, swivel. Attach the hooklength to the other side of the swivel. This should be around 3-6ft of 50-80lb monofilament line.
Thornback rays do not have teeth, but they do have incredibly strong, crushing jaws designed for dealing with crabs and shellfish, which will make short work of thin monofilament. Their round shape means they offer considerable resistance in a run of tide, which can result in inadequate hooklengths snapping.
Depending on the type and size of bait, the hooklength should terminate in either a single hook or a Pennell rig (two hooks in tandem). Hooks such as Sakuma 545 Manta Extra in size 4/0 to 6/0 are perfect.