Steel arches Step 1 Mark out post holes and dig to about 1m deep. Place posts into holes and secure in place using rapid set concrete. Ensure posts are vertical. Step 2 Cut horizontal beams to length using an angle grinder. Step 3 Erect scaffolding to provide a sturdy and level platform from which to work.
Clamp beams to posts at finish heights using timber supports and clamps.
Ensure all beams are at the same level using a water level. Electric arc welding is a highly specialised skill and is potentially very dangerous. Do not attempt structural work like this unless you are already experienced. Always wear full length clothing, leather apron and gloves and welding mask. Do not weld with children in the vicinity and warn others not to look directly at the flash.