The concept for this tool is derived from a Japanese tool called Yari-gannas
Yari-gannas (Spear planes) are Japanese ancient planes which were used pre "dai-gannas (modern planes with wooden blocks.)" Yari-gannas were used after Chounas (J style adzes) to further refine the flatness of the surfaces. I have reduced the size ( cutting base is 10mm long by 4mm at the widest section) to fit small detail work on relief rifle carving.
Here is a brief outline of the way I use this background detail tool. In #1, I have stabbed two conversing arcs and roughed some of the background away. #2 show the tool in context to the area being relieved. I use the tool in a sweeping motion, as it best fits the area. The critical element is keeping the base of the tool as flat as possible. #3 is a close up of the background cut away. When flat on the work surface, the handle and hand have clearance of the carving.
Sharpening
#4 is the flat base of the tool, this needs to be kept very flat. Do not change the base if at all possible.
#5 illustrates the two upper surfaces of the tool. When sharpening I blacken with a felt tip marker
#6 I am moving one of the two upper surfaces of the tool against a stone
#7 The face on the right side is now clean from the sharpening. By using marker on the surfaces, I can gauge the angle of the stone against the surface.
Should you have challenges sharpening or need the angles re-established, I will do that for you free if you pay the postage.