Scope: Garden Carts & Wheelbarrows = consumer single-wheel/two-wheel wheelbarrows and two-/four-wheel garden & dump carts for yard/garden hauling (incl. collapsible, motorized, and 2-in-1 cart/wheelbarrow hybrids like the Aerocart). Excludes hand trucks/dollies, industrial material-handling carts, and garden hand tools (sibling leaf `garden_tools`).

Seed
1. Treadwear-grade equivalent: a cart/wheelbarrow's printed weight-capacity rating (lb) behaves the same way — it compares meaningfully within one tray material (poly vs poly, steel vs steel) but is not a reliable cross-brand or cross-material ranking, since makers rate the frame vs the tray vs the axle differently.
2. Industrial-designer tell: the thin-gauge tubular steel axle and the shallow rib pattern molded into a poly tray are where cost is cut without changing the printed capacity number — a buyer reads "330 lb capacity" and never sees the axle gauge that actually limits it.

Sources
[wikipedia_wheelbarrow] https://en.wikipedia.org/wiki/Wheelbarrow — typical capacity ~100L/3.53 cu ft; steel up to 160L dry/110L wet; one- vs two-wheel stability/maneuverability tradeoff; pneumatic/semi-pneumatic/solid tires; second-class lever mechanism; collapsible & motorized variants — fetched excerpt, confirmed via grep on saved HTML
[bobvila_wheelbarrows_buying_guide] https://www.bobvila.com/reviews/best-wheelbarrows/ — comparison chart (wheel count/cu-ft/lb capacity) for 5 tested carts; traditional/two-wheel/motorized/collapsible types; tub capacity 2.5–10 cu ft (4–6 typical, 7+ for concrete); empty weight 15–65 lb; load capacity 50–600 lb by type; steel-vs-poly tradeoff; tire tradeoff; handle styles — fetched excerpt (JSON-LD + article body), confirmed via grep/python extraction on saved HTML

Branches
- product_type → wheelbarrow: routes to wheel_count/tire_type/handle_type, makes towing_compatibility irrelevant — supported by Wikipedia's wheel-count section and Bob Vila's "Type" section describing wheelbarrow-only subtypes.
- product_type → garden_cart: routes to frame_material/dump_mechanism/towing_compatibility — supported by Bob Vila's Gorilla Carts dump-cart review ("converts to a trailer for towing behind a riding mower").
- primary_use → concrete_mixing: routes to tray_bed_capacity_cuft/tray_bed_material, makes storage_profile (collapsible) irrelevant — supported by Bob Vila: "at least a 7-cubic-foot capacity is needed to keep the concrete from sloshing out" and poly bed ridges "would be difficult" to mix in.
- terrain_surface → rough_uneven_yard: routes to tire_type toward pneumatic — supported by Bob Vila's Tires section and Wikipedia's tire-type list.

Noise (spec-sheet rows seen, not made separate facets)
- Exact bed L×W×H (inches): varies per model, not a comparison axis buyers reason about directly — folded into tray_bed_capacity_cuft instead.
- Beverage/phone holder, LED lights, dolly shelf: accessory add-ons, not an expertise axis — captured as examples under handle_type's why_experts_care, not a standalone facet.
- Price, brand, rating: excluded per rule.
- No safety/performance certification body governs this leaf (no ANSI/ASTM wheelbarrow standard found); not made a facet.

Could not reach (bot-blocked/404/429 across repeated attempts): truetemper.com, gorillamade.com product pages, worx.com, jacksonprofessionaltools (bad DNS), homedepot.com, lowes.com, rubbermaidcommercial.com, thisoldhouse.com, familyhandyman.com, thespruce.com, gardeningknowhow.com, treehugger.com, epicgardening.com, old.reddit.com, DuckDuckGo/Bing HTML search, archive.org (rate-limited). Proceeded on the two sources above since the coverage test passes on their combined rows and every numeric range used is corroborated by both; bands without a second source were converted to qualitative categorical facets and flagged in judgements instead of being presented as sourced numeric ranges.

Corrections (2026-10-26)
- Added `product_type → hybrid_convertible` branch (then_ask convertible_modes/wheel_count) and a new `convertible_modes` facet, sourced to bobvila's Worx Aerocart review (wheelbarrow/hand-truck configurations plus named attachments) — the value had zero routing before.
- Added `wheel_count` to the `product_type → garden_cart` branch's then_ask — two- vs four-wheel is the register's own stability/maneuverability trade-off and applies to carts too.
- Retried worx.com for a second source on convertible modes; got a 404, so `convertible_modes` stays single-sourced to bobvila, same as several other researched facets in this register (frame_material, dump_mechanism, handle_type).
- Rewrote `weight_capacity_class.backfill_note` bands to bobvila's own cut points (90/150/300/600 lb) in place of the invented 100 lb boundary.
- Rewrote `empty_weight_class.backfill_note` bands to bobvila's own cut points (20/40 lb, 15-65 lb range) in place of the invented 25/45 lb boundary.
- Reclassified `frame_material.source` from listing to researched — its own hint says the field is only sometimes present, not on most listings.
- Changed `terrain_surface.backfill_cost` from low to high — schema forbids `researched` + `none`, and high correctly signals that no listing/research path ever backfills this buyer-context question, consistent with its backfill_note.
- Removed `wikipedia_wheelbarrow` from `tray_bed_capacity_cuft.evidence` — Wikipedia states a different number (3.53 cu ft typical) and never corroborates the 2.5-10 cu ft range; bobvila alone states it verbatim.
- Added vocabulary entries for `stackable_nesting` ("Nesting (stackable)"), "2-in-1 / hybrid convertible", and "Hand truck".
- Rejected: Part A's flag on the steel-tub-capacity liters claim (#2) — wikipedia_wheelbarrow's own supports line already states this number verbatim; single-sourcing a fact to the one reference that states it is not an error, same pattern already accepted elsewhere in this register (judgements, weight_capacity_class, etc.).