Often, when dealing with seams, a problem arises if a vertex shares more than one UV coordinate. LSCM UVs may not unwrap the model as expected. To solve this problem, Unwrap 3D Pro provides a handy tool called Mark Boundary VEdges By UV. This tool will mark all vertex edges by the UV boundary of the face selection. When a vertex edge is marked, it will be cut prior to unwrapping, allowing the vertices along that edge to have its own UV coordinates.

Here is a quick example of using the Mark Boundary VEdges By UV tool.

Let's say we wanted to unwrap a head model using LSCM UVs. Typically, we would use the Seam tool to mark the vertex edges where we want to unwrap, all by hand. A quicker way is to take advantage of the Mark Boundary VEdges By UV tool.
qt_lscm1.png
First, we need some quick UVs. Click Ctrl+A to select all faces, then click 2D Tools | UV Mapping | Spherical. The UVs will be unwelded, so weld them using 2D Tools | Weld UVs. Welding UVs is necessary to create a UV boundary:
qt_lscm2.png
Now, click Ctrl+A to select all faces again, then click Edit | Seam | Mark Boundary VEdges By UV:
qt_lscm3.png
As you can see, the UV boundary was converted into marked vertex edges. A magenta colored edge means that vertex edge is marked for cutting.

Now, click 2D Tools | LSCM UVs:
qt_lscm4.png
Our entire head model is now unwrapped. Note that we locked two boundary UVs to make the unwrapping more symmetrical.
qt_lscm5.png
That's it! If you have any other questions about LSCM UVs or marking vertex edges, please let us know.