rotating rotated 3d modelling objects

[sommerfellers]

Ive made a 3d modelling for interior furniture. the shape is simple but has many ways of rotation. ive been trying to make it back straight like when i opened up the autocad. i need to make it straight back like 0 degrees to x or y or z. its been too many 3d models ive made on this file, and theyre not straight so it makes me difficult to continue my work cause i cannot easily rotate my objects in a simple directions. any help?

[steve216586]

First, set the UCS to World orientation. Then move the object to 0,0,0 coordinates using a base point which is a corner at 90 degrees to another face/edge. Rotate the object using "By reference" selecting the corner as the base, then a point on one of the face's edge, then aligned to an axis.