The restraints described up to this point are required for APR calculations. However, there are also optional restraints which can be set. One optional type of restraints are flat-bottom potential restraints applied to keep the guest in the host binding pocket during the attach phase and help define the bound state. These set of restraints are referred to as "wall" restraints. Wall restraints are intended to help improve the calculations through quicker convergence, particularly for weak binders, and were only applied if the guest leaves the host binding site past a threshold during the attach phase. In addition, when these restraints are applied they do not contribute to the final binding free energy. For WP6, twelve wall restraints were set on the guest relative to the host carboxylate arms to keep the guest in the host binding cavity (defined by atoms O1, O31, O25, O19, 013, O7, O2, O32, O26, O20, O14, and O8). For the bCD and HbCD hosts, 7 wall restraints were set on the guests relative to the oxygen atoms (O3, O33, O28, O23, O18, O13, and O8) of each glucopyranoside linker. The parameters used for the wall restraints are shown in Table †.