A link anchor is a point on the paper that the link wants to reach as its endpoint. (In reality, the end element will probably be in the way - then, it will be the job of the connection point function to determine the actual location of the route endpoint taking the respective end element into account.) Anchors are set via an anchor property provided within link end definitions (i.e. the objects provided to link.source() and link.target() functions).

There are many built-in anchor functions in JointJS:

Example:

link.source(model, {
    anchor: {
        name: 'midSide',
        args: {
            rotate: true,
            padding: 20
        }
    }
});

The default anchor function is 'center'; this can be changed with the defaultAnchor paper option. Example:

paper.options.defaultAnchor = {
    name: 'midSide',
    args: {
        rotate: true,
        padding: 20
    }
};

JointJS also contains mechanisms to define one's own custom anchor functions.