To place nodes along the boundary of a block

Select Place Nodes.
Select the appropriate color mask.
From the Entity option menu, choose Line or Outline.
Select Block as the Boundary option.

Note: This option is not accessible when there is no active image.
Define the block to be used as a boundary by entering two opposite corners.
If Line is chosen, nodes are placed everywhere the boundary of the block crosses raster lines. Outlines or edges are not considered.

If Outline is chosen, nodes are placed everywhere the boundary of the block crosses the edge of raster objects or lines. Both sides of raster lines are considered.

Both Raster Snap and Vector Snap toggles are disabled with this option.