Hi, I was trying to draw a zig-zag closed spline on hemispherical surface, such that all 'peaks' and 'valleys' touch (preferably tangentially) two 'latitude' circles. No problem in building hemispherical surface, adding face (construction) curves for latitude / longitude reference, and adding spline itself. But when I try to make the spline touch the bottom circle using coincident relation, SW says it will invalidate the geometry thus impossible. I don't see why not. Can anyone help me out here? I am using Solidworks 2017 x64 edition, SP4.1. The part is attached.