I am trying to get rid of thick black line in Micro Soft Word
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You tagged your question common
: this means here the issue occurs in Writer, Calc, Impress, Draw, Base, and Math. If you target a specific application, please retag the question with the appropriate tag: writer
for text documents, calc
for spreadsheets, impress
for presentation, draw
for drawings, base
for database access, math
for the formula editor.