The conventional sidelobe blanking system, known as the Maisel sidelobe blanker, uses two receiving channels with different gains to detect the presence of a jammer. The Maisel system is an ad-hoc detector without any optimality properties. Yet, it has been successfully utilised in numerous operational systems. Here, the authors study the optimum Neyman-Pearson type sidelobe blanking (SLB) detectors for the Swerling target models to assist the design of Maisel blankers. The authors note that the optimal sidelobe blankers are of theoretical interest, since they require the knowledge of target and jammer parameters, which are typically not available at the radar site. The main goals of the present study are (i) to derive the optimal Neyman-Pearson detectors for SLB, (ii) to examine the performance gap between the optimal and Maisel detectors, and (iii) to develop objective criteria for the design of Maisel blankers that provides a guarantee on the gap to the optimality. Ready-to-use computer programs to assist the design process are also provided.