- At the lowest level of function candidates will have the ability or potential to use a prosthesis for transfers or ambulation on level surfaces at a fixed cadence. Typical of the limited and unlimited household ambulator, the majority of candidates' ability or potential for ambulation with the ability to transverse low-level environmental barriers such as curbs, stairs, or uneven surfaces (the ceiling for candidacy) will be those TTAs who have the ability to vary cadence and can ambulate within the community.