Yes, repair contracts will often include an option to apply a Mechanic's Lien. "In-possession" Mechanic's Liens are common. For example, if you drop off a ring to be repaired by a jeweler, but you don't pay or pick up the ring within a certain amount of time (they have possession of the ring). In this case, your jeweler will most likely sell your ring to recoup their costs. This option is written into the original sales contract. Most of us are aware of this type of lien and can and should write it into our repair contracts.
"Non-possession" Mechanic's Liens are a bit different. If you perform repairs on a customer's property but do not have possession of the property, you can apply a 'non-possession" type lien. In this case, you most often have to file with the local courts to enforce a Mechanic's Lien against the property. If the client doesn't pay, you may be allowed to reclaim the improved property. For example, if you put in new kitchen cabinets and are not paid, you may be able to take the new cabinets out of the kitchen to help recoup your costs.