Rivet — excellent brand meaning: something that holds things together, which maps nicely to managing jobs, schedules, customers, estimates, and invoices. Very memorable and practical. However, your brief explicitly says Rivet has already been ruled out, so I would not submit it.
Other entries by amar36 (2)
Mason — familiar, solid, hands-on, and strongly associated with skilled work and building, while still broad enough to represent contractors generally. The downside is that it has significant existing commercial/name usage, so it needs careful competitor checking.
Stout — short, real word, strong and dependable. It conveys durability and confidence without tying the product to a specific trade. Easy to hear, spell, and remember. Best overall fit.