Two ways to make a steel joint, both taking ½″ through-bolts clean through the 2×4: the one-piece Plate Hub in 3/16″ plate, pre-bent and ready — and the flat-pack Strap + Ring in 1/8″, shipped flat by parcel with twin-ring nodes and a bend you make yourself in a bench vise. Fasten each strut your way, screws-only to double-bolt with back plate.
Same plate, same bolts, same dome — different philosophy. These aren't drawings of the products; they're the actual cut files the laser runs.
The integrated option. Fewest parts, fewest fasteners, stiffest single node — the polygon core ties every tab into one piece of steel. Nothing to align but the dome itself.
The flat-pack option. Every part is flat laser-cut 1/8″ steel; each hub clamps its straps between two rings, so every ring bolt works in double shear with zero prying. You make one straight bend per strap in a bench vise against the included angle gauge — about 250 in·lb, genuinely easy — and the whole 3V kit arrives in parcel boxes instead of on a freight truck.
Plate Hub if you want it pre-bent, maximum node stiffness, and minimum shop time. Strap + Ring if you'd trade an afternoon at the bench vise for parcel shipping, field-replaceable parts, and rings that carry over if you ever build a different frequency. Strength-wise both put two ½″ through-bolts in every strut end — and for gauge context, the strap steel is 2–4× the thickness of the joist hangers holding up your house.
A 3V dome wants four slightly different strut angles at every joint. We bend everything to one universal 11.5° and absorb the difference deliberately: the outer bolt rides in the lateral slot, the inner hole is oversized for bolt tilt — ±9° available against a worst-case need of 2°. The dome pulls itself true as you tighten the ring.
Slip it over a strut end, drill through the guide holes, done — every bolt hole in the kit lands within the slot's forgiveness, all 330 patterns on a 3V dome. Included with every steel kit, both systems.
Every tab and strap ships with the full hole pattern cut — two ½″ bolt positions and a dedicated column of 5/16″ holes for ¼″ structural screws. How hard you fasten is your call, per strut, per build. In the drawings on this page: orange holes take bolts, blue holes take structural screws.
| Level | Per strut end | Drilling | Best for |
|---|---|---|---|
| Screws only | 3 × ¼″ structural screws (GRK / SPAX class) | None — driver only | Light covers, shade frames, temporary & event domes, fastest build |
| Single bolt + screws | 1 × ½″ bolt (inner hole) + 2 × ¼″ structural screws | 1 hole per strut end | Mid-duty: greenhouse film, canvas, seasonal structures |
| Double bolt | 2 × ½″ bolts (inner round + outer slot) | 2 holes — drill jig included | The standard spec — shelled and long-life structures |
| Double bolt + back plate | 2 × ½″ bolts clamped through a 2″ × 6″ steel back plate | 2 holes — drill jig included | Maximum joint: rigid clamp, no pull-through, moment-resisting |
The holes are in every part either way, so you can mix levels in one dome — double-bolt the base ring and lower courses where loads concentrate, run screws-only up top — and come back later to add bolts or back plates as the structure's job grows. The hub never has to be the thing you replace.
◆ Cut to order — steel kits typically ship in 2–3 weeks
One hub does not fit every position. A dome needs three different hub types — 6-way for the interior field, 5-way at the pentagon points, 4-way around the base — and every kit ships the exact mixed count for its geometry.
| Per kit | 1V | 2V | 3V |
|---|---|---|---|
| 6-way | — | 10 | 40 |
| 5-way | 6 | 6 | 6 |
| 4-way base | 5 | 10 | 15 |
| Total hubs | 11 | 26 | 61 |
| Rings (R series — 2 per hub) | 22 | 52 | 122 |
| Straps (R series) | 50 | 130 | 330 |
| Drill jig + bend gauges | 1 + set | 1 + set | 1 + set |
Same mixed counts in both steel systems — plate hubs and rings share the 4/5/6-way split. The three types are visually unmistakable (square-ish / pentagon / hexagon), so there's nothing to label or look up mid-build.
vs $399.99 list for the leading single-tab 1V kit
vs $599.99 list for the leading single-tab 2V kit
vs $1,399 list / $1,249.99 sale for the single-tab 3V — and R3 ships parcel, not freight
The leading single-tab steel kit cuts its 3V hubs from the same 3/16″ steel we use — as a 4″ core with 1.5″ × 3″ screw tabs. Our plate hub is a full polygonal plate with 6″ through-bolted tabs and anchor flanges at roughly twice the steel per joint, for $50 less — and our strap+ring matches their sale price with through-bolts they don't have. Bring a tape measure to the comparison.
One strap, every strut, every position.
Each strap lies on the 2×4 on edge: two ½″ bolts through the lumber (inner round hole locates, outer slot absorbs the angular spread), and a tapered inner tab clamped between a pair of rings — every ring bolt loads in double shear, with no single-lap prying anywhere in the node. The single bend per strap is the only forming operation in the whole system, and it's yours: 1/8″ steel folds at about 250 in·lb, a bench vise and a two-foot bar, checked against the included laser-cut angle gauge (11.5° for 3V; the same blank bends to ~17° for 2V, ~32° for 1V).
The rings are pure flat laser work — a 5.5″ annulus with 4, 5, or 6 bolt holes setting the hub geometry (90° / 72° / 60°), used in identical pairs. The 4-way base ring is cut flat on the floor side so the ring and the 2×4 bottoms land coplanar on your slab.
5-way ring · 4-way base ring (flat side down on the slab)
System C — the fork & deck. Nobody bends anything, anywhere: the dome angle is cut into the steel, not bent into it.
Each strut is gripped by a fork of two vertical fins whose strut seat is laser-cut at the dome angle — exact geometry, no springback, no brake at the shop, no vise at your bench. The fins tab into a flat deck plate and clamp with ¼″ bolts into captive nuts: you assemble the 61 hub "spiders" on the ground, sitting down.
Then the part we're proudest of: each strut gets a bolt slipped through it on the ground, and in the air you simply hang it — the bolt drops into a leaning J-hook on each fin and the strut dangles captive, hands-free, while you add the one remaining bolt. No holding lumber overhead, ever.
Status: validation parts are being cut now. If it proves out, it joins the lineup as the no-skill-required steel kit. Want to know when? Get on the list.
Sits on the far side of every strut end, spanning both bolts — turns two independent fasteners into one rigid clamp. No bolt-head pull-through in softwood, real moment resistance. Same bolt pattern as both the plate-hub tab and the strap, so it works with either system. 50 / 130 / 330 plates by kit.
Budget alternative: 1.5″ fender washers (~$0.10 each). They stop pull-through; they don't clamp.
Every flat-pack kit already includes the laser-cut angle gauges — a vise and a cheater bar is all 330 straps need. If you'd rather crank than check, the bench jig clamps in your vise with hard stops at all three angles: drop a strap in, pull to the stop, next. Buy it once, bend every kit you'll ever own.
Standard finish is powder coat over clean steel — good for covered and shelled structures. If your frame lives exposed (shade structure, coastal air, livestock breath all winter), hot-dip galvanizing buries every edge and bolt hole in zinc. Choose it once, never think about rust again.
Every kit includes a printed cutting chart with strut lengths and color codes for your dome size — cut, paint the ends, drill through the jig, bolt up.