1. The presented theoretical and experimental values of the coordinates of the surface of vacuum-free inlets (under actual conditions they can be with a weak vacuum) obtained from an examination of the discharge of water from under a gate under conditions of a plane problem can be used in appropriate cases when extreme vacuums or unfavorable transitional regimes in a conduit can occur in the presence of more compressed inlets; they deserve particular attention for short conduits. The values of the vacuum and cavitation characteristics must be determined later for these inlets. 2. Inlets of simple outline, including circular and especially elliptical, can be quite suitable under actual conditions in appropriate cases. The vacuum and cavitation characteristics presented in the article permit the evaluation of different inlets in a cavitation regime under different conditions. 3. On the basis of experiments carried out in an ordinary channel and in the cavitation installation we obtained values of the correction factors ζ′ for the vacuum coefficients determined by means of piezometers and gauges. Their values were small (no more than 1.04) which permits using not only the cavitation but also the vacuum characteristics of the inlet for predicting cavitation with sufficient reliability. 4. Rounding of the corners of the inlets improves their cavitation characteristics. 5. Investigations of the vacuum and cavitation characteristics of inlets of undersluices should continue, and problems of the scale effect and transitional regimes in a conduit should be studied.