People visit public places with different intentions and motivations. While some explore it carefully, others may just want to pass or are otherwise engaged. We investigate how to exploit the inattentional blindness (IB) of indirect users in the design of public interfaces to apply to such diverse needs. Beginning with a structured literature study in the ACM Digital Library on IB, we analyzed 135 publications to derive design strategies that benefit from IB or avoid IB. Using these findings, we selected three existing interfaces for information presentation on a large public square and created two additional interfaces ourselves. We then compared users' perceptions through a self-reported photography study (N = 40). Participants followed one of four scripted profiles to imitate different user intentions, two for direct and two for indirect users. We hypothesized that direct users would recognize the interfaces, while indirect users would experience IB and ignore them. Our results show that direct users reported up to 68% of our interfaces, whereas indirect users noticed only 16%. Thus, IB can be exploited to hide interfaces from indirect users while keeping them noticeable to direct users.