Here are three different design approaches we’ve seen for hand-trucking objects up and down stairs.
An approach used by UpCart and others uses a trio of wheels on each side:
The Techlift employs a pair of flip-down levers to provide leverage:
Those first two necessitate extra moving parts, and thus more risk of breakage. But this design by Matador simply uses tubing bent to a specific angle and protective slides:
From afar at least, I like the simplicity of the latter approach.