Good work, John. This really help.

@greatoe said: Can I draw a conclusion that to make two parallel arcs, I can only do it manually, either draw the two arcs one by one with the build-in arc command or use the scripts with fillet tool to form the arcs one by one? Yes.

@juanv.soler said: i understand your pain @didier bur said: Hi, Something like this ? [attachment=3:3py8nirk]<!-- ia3 -->bissectr4.gif<!-- ia3 -->[/attachment:3py8nirk] If we know the lines (even 2 of them parallel), we can calculate I, then create the circle. Do-able, but not now (too much work on other projects). Hi JuanV.Soler and D.Bur, Thanks for the reply, you understood me exactly. If I try to draw it manually (use only the primary sketchup drawing tools), firstly I draw circle A, get poit B and C, then I draw circle B and circle C with the same radius to get point D, line AD is the bisector of angle BA/AC, with the same method I have line EF, now I get point G, intersection of line AD and line EF, which is the center point of the circle I want (which tangent to the three lines) [attachment=2:3py8nirk]<!-- ia2 -->34.jpg<!-- ia2 -->[/attachment:3py8nirk] but as you can see in the picture, because sketchup use segments to form circles, obviously segment AB does not equal to segment AC, and line AD is not the exact bisector of angle BA/AC. within the script "k_tools.rb" by Klaudius there is a function call "Angle Division", this helps finding the exact biscetor of the angles, also the exact center point of the final circle, but problem still remains, [attachment=1:3py8nirk]<!-- ia1 -->35.jpg<!-- ia1 -->[/attachment:3py8nirk] I draw a circle from point G perpendicular to line AE, so T2 is the exact tangent (and intersection) point of the circle and line AE, T1 and T3 should be the other two tangent/intersection points, yet, again, because the circle is made by segments, I'm not able to get intersections of the circle and the lines. This is much clear with a circle with less segments, As shown in the above picture, the circle with less segments (12 of them) does not even touch the lines. And, normally we want a model with less segments, right? The following picture shows what I want/got finally. [attachment=0:3py8nirk]<!-- ia0 -->37.jpg<!-- ia0 -->[/attachment:3py8nirk] [image: BI7C_34.jpg] [image: UIYW_35.jpg] [image: xZy1_37.jpg]