For this tip, it is best if you sit down and try it on your own. It is one of those things that is better demonstrated than written out.

Take a look at the UCS:

In plan view (command: PLAN) when it is set to “World” it shows the Y axis pointing up and the X axis pointing left. This is very important to remember when using X and Y point filters. Looking at the UCS from this view, X point filters apply to the left/right direction along the X axis and Y point filters apply to the up/down direction along the Y axis.

The best way to explain point filters is to demonstrate them. Let’s say you have two lines such as this:

…and you want to draw another line above it that starts perpendicular to the right endpoint of the horizontal line.

Type the LINE command on the command line and you will get this prompt.

LINE Specify first point:

Type .X at the prompt:

LINE Specify first point: .X

Then it will prompt you with “of”.

LINE Specify first point: .X
of

Type END (or hold down shift, right-click and select “Endpoint”):

It will then prompt you for the Y and Z:

LINE Specify first point: .X
of END
of (need YZ):

Click anywhere in space above the right endpoint of the horizontal line.

Notice how the start of the line is perpendicular with the endpoint that you snapped to? This is because the X point filter held the X coordinate when you clicked in space.

The same works for the Y point filter. What’s even better is that you can use the X and Y point filters together. When it prompted you for:

LINE Specify first point: .X
of END
of (need YZ):

You could have typed .Y and clicked somewhere to hold the Y coordinate as well. Then when you click anywhere in space it will hold both the X and Y coordinates.