Many of the mesh tools involve selecting or manipulating nodes. Ensure that the nodes in the part are visible and selectable by activating the required layers in the Layers pane.
The 
Stitch Free Edges tool is used to merge together a pair of nodes that are within a certain distance from each other, and that form a free (unconnected) edge with a similar pair of nodes. The distance between the nodes to be merged is the tolerance, and the default tolerance is 0.1 mm. You can specify a tolerance of your choice if you want.
Use the 
Swap Edge command to exchange the edges of two adjoining mesh elements. The Swap Edge command works on triangular elements, however, it cannot be used on tetrahedral meshes.