If labor and management are trying to reach a compromise through collective bargaining and are unable to do so, there are a number of things that they can do.
The first of these would be to bring in a mediator. A mediator is something like a counselor. That person listens to what each side has to say. The mediator then tries to find ways to reduce the level of conflict between the two sides and to steer them towards a compromise that they can both agree upon.
The second step would be to bring in an arbitrator. This person is less of a counselor and more of a judge. The two sides submit their proposals to the arbitrator. The arbitrator then creates their own solution. The arbitrator imposes a solution on the two sides and the two sides must accept that solution.
However, the two sides are typically not required to submit to arbitration. Therefore, either side can decide to pursue a work stoppage. The union can go on strike. The management can lock the union out and essentially shut down operations, (the company can also try to do something like using management to keep a minimal level of production going). In work stoppages, the two sides are essentially betting that they can hold out longer than the other side.
These are the most common alternatives that can be pursued if management and labor cannot compromise.