Tie firmly a short segment of a fishing line through the middle of a plastic or wooden dowel and make sure it balances horizontally whenever you suspend it freely.
Hang your selected art pieces, shapes or toys from each end of the dowel. Distribute the weight of the items you are hanging on either side of the dowel to maintain the balance of the dowel. However, you may choose to place a heavier item on one end to make a unique design of the mobile. In case you have items of dissimilar weight, you can still make the whole structure balance by tying the fishing line that suspends the mobile closer to the end holding the heavier item.
Bind the other end of the fishing line on the dowel to a cock. Stab the cock with the axle of a motor then apply some glue at the piercing so that the whole mobile is firmly joined to the motor.
Fix the motor either on the crib or on the ceiling above the child’s crib but within the baby’s view. Use a screwdriver to fasten the motor onto its support. For safety reasons, when installing a mobile for your baby, you can only place it directly above the crib during the time before your baby starts sitting on her own or else you child may bump her head in the mobile, if it's too close.