Step 1 Decide on location and length of your screen. Lay out plastic panels side-by-side and set out end posts. End posts need to be flush with outside edges of end panels. Using post hole digger, dig 500mm-deep holes in each end position.
Step 2 Place 1 end of 1 post into 1 end hole. Strap post leveller to post and ensure bubbles on both sides sit evenly between lines. This means post is plumb in both directions. With a helper holding post in position, pour water and concrete into hole and mix, following product instructions. Check again for plumb and leave to set. Repeat for other end post.
Step 3 From outside of 1 end post, measure in width of panel (here, 1205mm) and mark with set-out paint. This will be centre of next post. From there, mark every panel width for centres of remaining posts. Dig 500mm-deep holes at these marks.
Step 4 Run a taut stringline between end posts at top and at bottom. Place a 10mm packer between post and stringlines at each end. Place remaining posts into holes. Using a packer as a guide, position other posts so they are 10mm from stringlines at top and bottom. (This gap prevents 1 of the posts from fouling the line and sending your screen off course.) Ensure posts are plumb, then add concrete and leave to set as in Step 2.
Step 5 From ground level of 1 end post, measure up height of panel (here, 2450mm) and mark. Transfer this level on all other posts, then use power saw to cut tops off posts at these marks, if needed.
Step 6 Cut rails to fit between posts at top and bottom. Make top rails flush with top of posts. Then measure down posts length of panel for position of underside of bottom rails. Using nail gun, skew nail rails in place. Paint posts and rails. Let dry.
Step 7 Clamp 1 panel to 1 end post so it is flush with post at top and side. Countersink and screw panels to posts and rails. Repeat for all other panels, ensuring they are aligned.