The　numerical　manifold　method　(NMM)　provides　a　general　framework　for　simulating　both　continuities　and　discontinuities.　By　cutting　covers,　NMM　can　adopt　a　regular-shaped　triangle　(or　quadrilateral)　for　interpolation.　This　brings　advantages　of　the　best-shaped　mesh;　however,　it　also　leads　to　some　issues　in　displacement　boundaries.　This　study　shows　possible　issues　and　related　treatments　on　boundaries　inaccuracies　in　NMM:　(1)　constrained　partial　edges,　(2)　cumulative　errors,　and　(3)　boundary　changes　in　contact　iteration.　In　NMM,　constraining　a　part　of　the　edge　will　constrain　the　whole　edge,　and　therefore　bring　additional　stiffness.　This　error　can　be　avoided　by　a　new　load-spring　control　method　or　adjusting　the　NMM　mesh.　In　dynamic　NMM　analyses,　penalty　springs　reapply　at　every　time　step,　and　they　only　constrain　incremental　displacement.　As　a　result,　cumulative　errors　should　be　avoided.　If　time　step　interval　changes　in　contact　iteration,　moving　boundaries　need　to　be　renewed.　This　paper　also　provides　general　formulas　for　displacement　boundaries,　the　necessary　and　sufficient　condition　for　line　constraints,　a　load-spring　control　for　full　load-deflection　responses,　and　a　robust　scheme　for　moving　boundaries.