How it all fits together

Once you understand the six core concepts, the flow through the app makes sense at a glance:

Price Sheet (PDF/Excel)        Manual entry
        │                            │
        ▼                            ▼
     Products  ──►  Prices  (per supplier, per date)
                       │
                       ▼
                  Assemblies  (recipes that combine products)
                       │
                       ▼
                    Rates   ◄──  Takeoff quantities
                       │
                       ▼
                   Estimate  ──►  Excel export

Reading the flow

Products are the master list of things you buy or supply. Populate them either by importing supplier price sheets or adding them manually.
Each product accumulates Prices — one per supplier, per effective date. Old prices stay in history.
Assemblies combine products into reusable recipes (e.g. “150 mm reinforced slab per m²”).
Rates are the per-unit prices on each estimate line. They can be typed directly or computed from an assembly.
Takeoff quantities (measured off drawings) supply the how much; rates supply the how much each.
The Estimate brings it all together and exports to Excel.

What changes automatically

Update a supplier price → next time an assembly using that product is applied, the new cost flows through.
Re-measure a takeoff shape → the group quantity updates → the estimate line total updates automatically.
Change a variable when applying an assembly (e.g. {thickness}) → the rate recomputes for that one line, without touching the assembly itself.

What doesn’t

Editing an existing price record updates it in place — use this only for typos. To record a price change, add a new price so history is preserved.
Excel exports are snapshots. The file you send today won’t change if your rates update next week.