Sometimes a project can only be successfully built on a particular slave (or master). If so, this option forces Jenkins to always build this project on a specific computer. If there is a group of machines that the job can be built on, you can specify that label as the node to tie on, which will cause Jenkins to build the project on any of the machines with that label.

Otherwise, uncheck the box so that Jenkins can schedule builds on available nodes, which results in faster turn-around time.

This option is also useful when you'd like to make sure that a project can be built on a particular node.