Start with the opening, not the gate

Before you cut a single bar, measure the gap the gate has to fill. On most small British gardens that means a space between two posts somewhere between 850mm and 1,000mm wide. Measure at the top, the middle and the bottom, because brick piers and timber posts are rarely true, and take the narrowest reading as your starting point. A gate that fits the widest measurement will jam where the gap tightens.

Allow roughly 10mm of clearance on each side, and a little more if the gate swings over uneven paving or gravel. Depth of the post matters too: a gate is only as rigid as what it hangs from, so set posts at least 600mm into the ground, bedded in concrete, with the hinge post slightly heavier than the one carrying the latch. If you are forging for a friend, ask whether they want it hung to swing inwards over the path or outwards towards the lane. Outward-swinging gates clear flower beds and boot scrapers, but they need a stop or a chain to prevent them banging back against the wall.

Proportions that quietly work

Traditional garden gates tend to look right when the proportion sits somewhere near three to one. A 900mm wide gate at 900mm high reads as squat and cottagey; the same width at 1,100mm high feels more formal. For a small garden, 900mm wide by 900mm high is a safe, honest size, and it is light enough for one person to lift on and off its hinges without help.

The frame does most of the structural work. A common arrangement is a 40 x 10mm flat bar for the top and bottom rails, with a 12mm square bar for the verticals, or stiles at each end if you want the gate to look framed. Keep the spacing of the uprights at no more than 100mm apart, partly for looks and partly because a gap wider than that will let a small dog or a determined toddler through. If the gate sits at the top of steps, close the spacing further.

• Top rail: often set with a gentle rise in the centre, about 25mm over a metre, which stops the eye reading it as a sag.
• Bottom rail: lift it 75-100mm off the ground so wet grass and leaf litter do not sit against the iron.
• Brace: a diagonal from the hinge bottom corner to the latch top corner carries the weight and stops the frame racking.

Scrolls without clutter

Scrollwork is where a simple gate either sings or turns into a tangle. The trick is repetition. Pick one motif, cut it in card or thin ply, and hold it against the frame before you commit to the forge. A single S-scroll in the top panel, mirrored on both sides of the centre, will do more than five different shapes competing for attention.

Small British gardens reward restraint. Keep the bottom two-thirds of the gate as plain verticals, and reserve the decorated panel for the top third where it is seen against the sky rather than against a hedge. Watch the tightness of your curls: scrolls smaller than about 40mm across are fiddly, catch on sleeves, and collect cobwebs. If you draw down a fishtail on the end of a scroll, keep it blunt rather than needle-sharp, since gates are handled daily and knuckles find every point.

Forged tenons and rivets, rather than a fully welded frame, suit traditional work and give a little movement in the joints as the gate expands and contracts. If you weld, weld both sides of every joint and dress the seams flush so water cannot pool in a crevice.

Hinges, latches and the way it swings

For a gate of this size, band-and-gudgeon hinges are the traditional choice and still the most reliable. The gudgeon — the pin — is fixed to the post; the band is riveted or bolted to the gate's hinge stile. Place the top hinge just below the top rail, and the bottom hinge around 250-300mm up from the bottom rail. If the gate comes out wider than 1,200mm, or heavier than about 20kg, add a third hinge in the middle to stop the frame dropping.

Hang the gate so there is roughly 5mm of lift at the latch side, which sounds generous but accounts for the sag that appears as the hinges bed in. Fit the latch on the free stile at about 1,000mm from the ground, or lower if children will be using it, and pair it with a drop bolt if the gate is likely to be left open in wind. A small spring or a counterweight will bring it closed on its own, which matters more than most people expect on a slope.

Weather, rust and what you finish with

Mild steel will rust in a British garden within a season if it is left bare, so decide on your protection before you start forging. Hot-dip galvanising gives the longest service, but it needs the gate to be built with drainage in mind: drill a small weep hole at the lowest point of every enclosed section so the molten zinc, and later rainwater, can escape. If galvanising is not practical, a zinc-rich primer followed by two coats of a micaceous iron oxide or a good metal paint will last many years.

Rust begins at edges, welds and the insides of joints, so prime those areas first and work outwards. Paint the gate before you hang it, touching up the hinge fixings afterwards. Use stainless or galvanised bolts rather than plain steel ones, which will stain the paint with rust streaks. A wipe of linseed oil on the scrolls each autumn keeps the surface sealed and lets you spot damage early, before a small patch of rust becomes a hole.

Fitting day and the small details

Set the gate on packing pieces so it clears the ground by 50mm, check the diagonal measurements from corner to corner to confirm the frame is square, then fix the hinges. Pack the bottom hinge slightly out from the post if the gate needs to lift at the latch. Finish with a gate stop on the latch post so the gate cannot swing through and damage its own frame, and a gravel or concrete pad beneath the swing path to keep mud from splashing the bottom rail. A well-made iron gate, cared for, will outlast the fence beside it and the gardener who hung it — which is exactly the point.