CAD Designer Beau Bebout shares an in-depth description of creating blocks that utilizes the Wipeout feature in AutoCAD to assist in cleaning up your linework.
"This tip explains how to insert a block over a line — or any other object — without trimming the line or object underneath the block. It also allows annotation of blocks that will automatically change scale depending on the scale of the viewport or drawing. This technique is great for inserting valves into a piping or plumbing drawing.
"First, start out with a block that will require you to trim the pipe or line once you insert it into the drawing on the pipe/line. Next, create the block by typing Block on the Command line and selecting the objects. If it is already a block, double-clicking on the block usually does the trick. Once the block is created, open it in the block editor by selecting the block and typing Bedit.
"After you have it opened in the block editor, construct a closed pline around the area that you would like to be trimmed when inserted onto the pipe/line. (Note that you can draw outside the lines when creating this boundary, as it can be turned off; I will explain later.) Next, type in Wipeout. When asked for Frame/Polyline, type P (for polyline), then select the polyline you just made.
"Once you select the polyline, you may delete it or keep it. I usually type Y to delete it because I am editing existing blocks and copying over the existing lines with the polyline. If you delete it, there will still be a frame you can turn on or off later. Another reason to delete it is if you are updating any blocks with circles or anything that cannot be turned into a pline, as the Wipeout command only works with plines, and you will need to create your own boundary that you won't want to show up once inserted.
"Next, type Wipeout in the Command line, type F for frames, then Off to turn the frames off. This will turn off all of the wipeout frames, which can be done in the block editor or in model/paper space. While you are still in the block editor, select the entire block and type Draworder and F to bring the entire block in front of the wipeout.
"At this point I would typically set the block annotation to Yes in the properties dialog box so the block will automatically change size no matter what the scale of the drawing is. This step is optional, and I will not go into details of annotation here (as it could take many hours). You can bypass annotating it by using the old standby of just scaling it every time you insert it.
"You may now exit the block editor (after saving everything!). Once inserted/copied into a drawing, ensure that the block is in front of the pipe/line you are inserting it on; otherwise, the line will show through. Use the Draworder command, as we did a couple of steps ago, to be sure the line is wiped out."
Notes from Cadalyst Tip Patrol: This tipster has shown us how to create a block that covers, or masks, the linework underneath it using the Wipeout command. A wipeout will create a blank area in your drawing without altering the linework in the file. Beau has placed wipeouts in his blocks that represent pipe fittings. The wipeout covers the linework of the pipes in order to better visualize the symbol.