I want to put a border line around a cell.
@DaveCurrie: what is a cell in Draw (your question tag)?
A bit more detail are needed…
Please edit your question to add information (answers are for solutions only).
If your question is related to the Calc cells, then use the Cell Styles: adjust the border in the applied (user defined) Style.
If your question is related to the Draw rectalgle objects, then use the Object Styles: adjust the border in the applied (user defined) Style.
If your question is related to the Draw Tables, then adjust the border in the Table properties: