Draw lines with the Line tool

Select the  Line tool () from the toolbar. If you can’t find the Line tool, select and hold the 
 Shape tool ()  to show the other related tools, and then select the Line tool.

To create a line as a shape, choose Shape mode in the Options bar and then set the Stroke and Weight. 

To create a pixel line, choose Pixels mode in the options bar and then set the Weight. 

To create a path, choose Path mode in the options bar and then set the Weight. 

Select the canvas, drag, and release to create a line. To constrain the line angle to a multiple of 45 degrees, hold down shift as you drag and draw the line.