The first objective with this type of puzzle is to take it apart, which is usually the easiest part. The second objective is to put the pieces back together again, which is normally much more difficult. The difficulties generally arise because the puzzler can often see where the pieces ought to go but finds another piece preventing it being placed in that position. The skill is working out the method and correct order to put the pieces together. The other difficulty can be forgetting what the original shape looked like, so a picture of the original is included in the instructions.