Despite being increasingly popular, many public touchscreen devices are not accessible to blind users. We present Toucha11y, a working prototype that enables blind users to use inaccessible touchscreens by themselves. Toucha11y consists of a mechanical bot that can be instrumented to an arbitrary touchscreen by the blind user and a companion app on their smartphone. The bot, once attached to a touchscreen, will recognize its content, retrieve the corresponding information from a built-in database, and render it on the user’s smartphone. A blind user can thus access the content and make selections via a smartphone’s built-in accessibility feature. The mechanical bot will automatically locate and trigger the corresponding virtual button on the touchscreen. We present the system design of Toucha11y, along with a series of technical evaluations. We conclude with a user study with ten blind participants, confirming that blind users can operate touchscreen devices with Toucha11y.