Dragging your cursor from left-to-right when selecting items behaves differently when you drag from right-to-left.
One of SketchUp’s most helpful features is also one of the least visible. It can even be frustrating if you don’t know what’s going on. And that feature is the direction of the drag when you select items.
The difference is this:
When you drag from left-to-right, only everything that is completely in the bounding box you’ve drawn will be selected. SketchUp refers to this as a “window selection.” Only items completely in the “window” you draw will be selected. If an object, geometry, or a component is on the line (but not completely inside of the box), it will not be selected.
When you drag from right-to-left, everything that is inside or touches the box you’ve drawn will be selected. SketchUp refers to this as a “crossing selection.” Any item crossing your lines will be selected. If an object, geometry, or a component is on the line, it will be selected.
Window Selection Example
Crossing Selection Example
When to use
Knowing the difference can be very useful when selecting difficult items.
The window selection can be helpful when selecting components that are confined tightly or nearby other components. Using a window selection, you can select the component without selecting its neighbors. In the example below, you can see how this window selection can be used to select a dowel between two pieces.
The crossing selection can be helpful when trying to select large objects. Instead of zooming out to make sure you can draw a box that encompasses the entire component, you can simply draw a crossing section that includes that component.
Crossing selections are also helpful for selecting guides. You cannot select a guide with a windowing section, because guides are of infinite length. No matter how far you zoom out, the line will continue. And selecting guides by trying to click on the narrow line is tedious. But a crossing section can be used to quickly select multiple guides for deletion.