Convert an object
Convert the poly lines to “building lines” (=lot boundary) and maybe “setback lines” (= additional distances to neighbours or inside of the building area). Select the future desired type of border in the tool bar. Press letter “f” on the keyboard.”Enter”, click on the lineto be changed. Finish command with right mouse click. The original poly line will be saved but can be deleted if wished. The detailed properties of each line appear when activated as an info on the properties bar and there they can be set individually. (On demand see the detailed description of the line types by going to help)