Two ways to make a steel joint, both laser-cut from 3/16″ hot-rolled plate, both taking ½″ through-bolts clean through the 2×4: the one-piece Plate Hub, and the modular Strap + Ring. Fasten each strut your way — from screws-only to double-bolt with back plate — with the drill jig included for the bolted levels.
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 modular option. The bend lives on the strap, the hub valence lives on the ring — so the rings never change between frequencies, every part stacks dead flat for shipping, and any single piece can be replaced for the cost of one strap.
Plate Hub if you want maximum joint stiffness and minimum hardware shopping. Strap + Ring if you want cheaper shipping, field-replaceable parts, or think you might build a different frequency later — the rings carry over, you just buy new straps. Strength-wise both put two ½″ through-bolts in every strut end; neither is the budget compromise.
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.
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 / rings | 11 | 26 | 61 |
| Straps (R series only) | 50 | 130 | 330 |
| Drill jig | 1 | 1 | 1 |
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
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 that bolts to the ring's bolt circle. The single 11.5° bend at the transition is the only forming operation in the whole system.
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°). 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)
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.
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.