Adobe Photoshop's powerful toolset allows users to create all sorts of digital images with ease. Formatting text, manipulating photos or preparing documents for publishing is relatively simple with this dynamic software application. Photoshop has a built-in tool to create shapes and lines. With this tool, you can create a thin horizontal line in just a few steps.
Launch Photoshop and open the document to which you would like to add lines.
Select the "Line" tool from the toolbox. You might have to hold and click the "Rectangle" tool to bring up a menu; then you can select the line tool.
Choose the color of your line by clicking the front color at the bottom of the toolbar and selecting a color of your choice.
Make sure "1 px" is the value in the "Weight:" box at the top of the page. This value determines the size of the line.
Drag your cursor to the place in the document where you would like your horizontal line to start. Hold down the "Shift" button and click and hold your mouse; drag your cursor to the right to create the line. Let go of the mouse when the length of your line is satisfactory.