Snap and lock tools are frequently used in conjunction with drawing tools, to enable the accurate placement of entities.
Snap Modes
The Snap tools allow you to change your snap mode, allowing you to modify the behaviour when you pick points on the project.
Most snap modes are indicated by a change in the cursor shape. You can use snap modes in conjunction with most tools which require you to pick points.
You can configure the snap behaviour via Draw>Snap>User Settings or via the Snap Settings toolbox (Window>Standard Toolboxes, Snap Settings). You can also configure Snap Settings Master Tool Settings.
Most of the snap modes are one-pick snaps - that is one pick on the drawing will result in one position for whichever drawing tool is active. However some of the snap modes require two picks, again resulting in just one position for the drawing tool. The two-pick snaps are: Intersection 2, Median, XofY. These snap modes show a message in the Snap Messages area of the Status Bar to indicate whether the tool is waiting for the first pick or the second.
You can also modify the behaviour of drawing tools using lock tools. Snap tools and lock tools can be used together.
If you wish to enter coordinates directly from the keyboard, you can do so via the Keyboard Entry toolbox.
Lock Modifiers
Lock modifiers can be used in conjunction with snap modes. They allow you to restrict the coordinates of a point, forcing it to be horizontal, vertical or orthogonal to the previous point(s) entered.
Related topics: Snap tools, Lock tools.