So you wanted to add some stripes or lines to your walls ..Well with new inventions of tapes just for this type job makes the job much easier..In photo here is edge lock blue painters tape..Another brand which has variations of tapes for age of paint..Frog tape is very good brand also……So here is great tip which makes these type of tapes work … First thing is get yourself a damp cloth/rag..Sd you mark off area you want to tape I lightly dampen the area before applying the tape..then real important part is after you have your line taped once again take your damp cloth and  run along the tape edge which seals the tape to the wall.. I take damp cloth and rub along tape in a massaging  action ..these tapes have glue on back that reacts with water to make a seal..After I paint the stripe and happy with paint coverage I remove tape immediately before that paint dried…just remove very slowly .. If there is any slight bleeding which can still happen on tougher walls. Just do quick touch up