How to make a concrete bench
Step 1.4 Assemble the leg forms

Sandwich the (e) pieces between the plywood (b) pieces.
Position the pieces in place (refer to the drawings on the previous page) and hold them there with clamps.
In all, there will be two leg forms, each consisting of two (e) pieces and
two plywood (b) pieces.
The plywood (b) pieces are already marked for drilling. That was done in Step 1.3.
Drill through the leg forms on each drill mark.
Use a ½" (12mm) diameter drill-bit to drill the holes. The bolts are ⅜" (10mm) diameter. The bigger hole enables the bolts to be easily inserted and removed.
It is important to make the holes approximately ⅛" (2mm) bigger in diameter than the bolts to ensure that they (the bolts) can be removed easily when it's time to release the form-work.
When the holes are drilled, you can then insert the galvanized ⅜" (10mm) hex bolts into the holes, add the washers, screw on the wing-nuts, and tighten.
Next screw a 4" x 2" x 2"wide (100mm x 50mm x 50mm wide) *galvanized angle bracket (or similar) to each end of each leg form. Four brackets in all.
Use only three screws to hold each bracket, as they will have to be unscrewed when it's time to release the form-work.