Rectangular regions of polygons, boxes, and wires can be erased or ``yanked'' with the erase button. The user clicks twice or presses and drags to define the diagonal of the region to be erased. Selected objects are not erased. Wires maintain a constant width, and are cut at the points where the midpoint crosses the boundary of the erased area.
In physical mode, if the Shift key is held during the operation termination (click or button release), there is no erasure, however the pieces that would have been erased are ``yanked'', i.e., added to the yank buffer. The pieces are also added to the yank buffer when actually erased. The yank buffer chain has a depth of five, meaning that the contents of the last five yanks/erasures are available for placement with the put command.
Geometry in ``foreign'' windows can be yanked. These are physical-mode sub-windows showing a different cell than the current cell being edited (as showing in the main window). The foreign window is never erased (i.e., holding Shift is not necessary), but the structure that would be erased is added to the yank buffer. Thus, one can quickly copy a rectangular area of geometry from another cell into the current cell, by yanking with erase and placing with the put command (below erase in the side menu).
The SpaceBar toggles ``clip mode''. When clip mode is active, for objects that overlap the rectangle defined with the mouse, instead of erasing the interior of the rectangle as in the normal case, the material outside of the rectangle will be erased instead. The overlapping objects will be clipped to the rectangle. This applies whether erasing or yanking, again the yank buffer will acquire the pieces that would (or actually do) disappear in an erase operation.
When the Ctrl key is held before the box is defined, clicking on a subcell will cause the subcell's bounding box to be used as the rectangle. Thus, objects can be easily clipped to or around the subcell boundary. This applies when yanking as well. The standard erase is the inverse of the subcell paint operation in the box command.
While the command is active in physical mode, the cursor will snap to horizontal or vertical edges of existing objects in the layout if the edge is on-grid, when within two pixels. When snapped, a small dotted highlight box is displayed. This makes it much easier to create abutting objects when the grid snap spacing is very fine compared with the display scaling. This feature can be controlled from the Edge Snapping group in the Snapping page of the Grid Setup panel.
The box, erase, and xor commands participate in a protocol that is handy on occasion.
Suppose that you want to erase an area, and you have zoomed in and clicked to define the anchor, then zoomed out or panned and clicked to finish the operation. Oops, the box command was active, not erase. One can press Tab to undo the unwanted new box, then press the erase button, and the erase command will have the same anchor point and will be showing the ghost box, so clicking once will finish the erase operation.
The anchor point is remembered, when switching directly between these three commands, and the command being exited is in the state where the anchor point is defined, and the ghost box is being displayed. One needs to press the command button in the side menu to switch commands. If Esc is pressed, or a non-participating command is entered, the anchor point will be lost.