In Fragmenstein, it is possible to enforce derivative atoms to map to specific atoms from the hit atoms in order to get the intended placement. An example of this is a parent hit with a ring in a flipped conformation. Crystallographic structures generally consist of a single conformer bound in a set orientation as suggested by the electron density map. In some cases, for example with the terminal amides of glutamine or asparagine or the ring in a histidine, the specific density alone cannot reveal which way these sidechains are oriented. This can apply to ligands . An example of this is seen with tubulin inhibitor Todalam-4 . This compound is the merger of two compounds (F04 and F36). One possesses an aminothiazole ring placed in one orientation in the crystal structure, yet for the merger to be accurate, the flipped orientation is required. When applied to this test case, when passed a map to override certain atoms Fragmenstein correctly predicts the intended placement (Figure ). This ability to fine tune the behaviour of Fragmenstein allows it to be highly versatile and adaptable. In the NUDT7 study, the two hits NU181 (in lavender, LHS) and PCM0102716 (puce, LHS) were merged in <paper> yielding the merger NU443. The crystal structure of NU443 (turquoise, RHS) overlayed with the placement predicted by Fragmenstein (green, RHS). PCM0102716 and NU443 are covalent with Cys73 via a acryloyl warhead. Internally outside of the PyRosetta operations, covalent attachment atoms are stored as dummy/R/✱ atoms, shown in white. The RMSD between the placed model and the crystal structure of NU443 is 0.28 Å, while the combined RMSD values of the model and the structure against the parent hits are 0.65 and 0.61 Å. In the placement process the hydroxyl of NU181 was automatically discarded from the mapping as it would otherwise impede the mapping of the second hit (PCM0102716) due to the greater proximity of the NU181 hydroxyl to the oxygen of the acryloyl warhead of PCM0102716 rather than to the carbon bonded the benzene ring in PCM0102716.