Why a pose?
Image maps are essentially flat things and 3D objects are not. If we can temporarily flatten out the surface of a 3D object so the image can face all the patches evenly, the image will appear less distorted. Generally, this flattening is something you do manually in a pose by moving CPs.
However, for uniformly round objects like your hammer head, cylindrical application is easier and more precise. You image needs to be painted so that the left and right edges can meet without an obvious seam.