The next day
All of the eight posts are now firmly set in place but the tops need to be trimmed off. (Remember, all the posts were longer than we needed!)
Measure from the ground 2200mm up one of the posts (we are assuming the ground is reasonably level) and mark with a pencil. With your set square, draw a pencil line around all four sides of the post (2200mm from the ground). You will probably need a ladder or saw stool to do this.
Now, hammer a 90mm nail partly into the outside edge of the post you have just marked on the underside of the pencil line. Sit one end of a level on that nail and hold the other end level against the next post. Mark the underside of the level with a pencil on the second post, checking of course, that your level is level, too! If your level is not long enough to span from one post to the next, get a straight piece of timber 1000mm long, and use that with the level sitting on top.
With your set square mark a pencil line around all four sides of the second post, and again hammer a 90mm nail partly in, the same as on the first post. Repeat this action until all eight posts are marked. Check that the pencil line on the last post is level with the line on the first post. If not, go around again with the level and find the discrepancies.
Trimming the posts
Cut off the top of the posts where you have marked, with a circular saw.
If the circular saw does not cut all the way through the post, finish the cut off with a handsaw.
Make sure you have firm footing and if necessary, erect a scaffold about 600mm off the ground.
For the head beams you will need eight pieces of timber 100x100 and 1000mm long. (Rough sawn treated pine, suitable for outside use.)
Pencil a square line at one end of the beam with your set square as on the diagram below and then pencil another line 22.5 degrees from the first.
Cut on this line with your circular saw.
If your circular saw does not cut all the way through the beam, finish the cut off with a handsaw.
Measure from the long point and along the beam 920mm and do the same cut that end as you have done the other end.
Another cut is required, this one 50mm square to the edges just cut.
To achieve this, hold your set square against the newly cut edge and slide it along until you are able to pencil a line 50mm long, square to the cut edge and finishing at the beams longest (face) edge.
Sounds complicated I know, but just follow the drawing in the circle.
Also see fig 4. Repeat this for all eight beams.
You now have all eight beams ready to sit in place.
Sit the eight head beams on top of the eight posts, see fig 4 and skew nail beams to posts with 90mm galvanized jolt head nails.
Nail a 300mm long metal strap plate to the top side of each head beam join. (Also see fig 4.)
This will stop any outward movement of the gazebo.
Nail the metal strap plates with 50mm clout head (flat head) galvanized nails.