Confirm intended use and size
A commuter, road, mountain, cargo, and children's frame face different demands. Use the maker's size and intended-use documentation, not a single height label, to decide whether the design suits the rider and riding conditions.
Map every interface
Record the head tube and headset standard, bottom-bracket shell, seatpost and clamp sizes, axle system, brake mounts, wheel and tire clearance, derailleur mounting, cable routing, and approved accessory mounts.
Review limits and documentation
Ask for geometry drawings, assembly instructions, torque requirements, rider and cargo limits, testing or compliance information where applicable, serial-number method, warranty, and replacement-hardware details.
Inspect before assembly and riding
Do not use a frame with cracks, major dents, distorted interfaces, damaged threads, severe corrosion, or unknown structural repairs. Structural evaluation and bicycle assembly should be performed by a qualified professional.