You can connect two entities with an arc of a specified radius to create a rounded edge. You can fillet pairs of line segments, straight polyline segments and arcs. To use this select 'Fillet' from Modify menu bar or select icon from Editing toolbar.
Steps to Fillet the two Entities :-
Select the Fillet tool from tool bar.
Specify the 'Fillet Radius' in Input toolbar.
Select the first entity (L).
Select the second entity (M).
1. Entity 'L' And 'M' to be fillet
2. Fillet between Entities.
In above fig.1 'L' and 'M' are two entities which to be fillet. To do fillet do all steps as described above and you will get fillet between these two lines as shown in fig. 2.
You can also make fillet in other way. This is useful while tracing curve edge of template. For that follows the steps as below :
You can fillet entity pair as Line-Line, Line-Arc, Arc-Arc.
Note: Also remember when you fillet the spline it will be changed to a polyline.