You can create a transparent opening in a filled object by joining two or more closed and overlapping objects to make a compound object or composite path. The parts which overlap will be unfilled, making holes through which you can see objects behind them. If the objects do not overlap, no holes will be created but the objects will still become one object.
Compound Object vs Composite Path
Compound objects and composite paths allow you to achieve similar results, but they have different effects on the objects:
Compound Objects: When you join objects into a compound object, the original objects are unchanged. To edit the subobjects, you must split the compound object. When a compound object is split, the original objects will remain.
Composite Paths: When you merge objects into a composite path, they are converted to paths and then merged into one path. Each former object becomes a subpath of the new composite path when merged. The subpaths can be edited with the Reshape tool. When a composite path is split, a path for each former object will remain.
For example, if you select a box and an ellipse together and choose Join Objects, and then later split the compound object, you will still have a box and ellipse. But if you had chosen Merge Paths instead and then split the composite path, the former box would be a path of four line segments, while the former ellipse would be a path of four curve segments.
Do not use compound objects or composite paths if you simply want to keep a set of objects together because PageStream and PostScript are limited in the number of points that can be used in one path. Use the Group command to manipulate objects as one, or use the Make Drawing command to make them into a drawing object.
Objects to be joined or merged must be unlocked and ungrouped. They cannot be drawings, pictures, EPS illustrations or text block. Note that a compound object or composite path has only one set of line, fill and color attributes. If you join or merge objects of different colors, the compound object or composite path will take on the attributes of the bottom object.
To create a compound object: Select the objects with the Object tool. Choose Join Objects from the Object menu.
After joining objects, size handles will appear around the bounding box of the new compound object. The compound object can now edited as a rectangular object with the Object tool.
To create a composite path: Select the objects with the Object tool. Choose Merge Paths from the Object menu.
After merging paths, size handles will appear around the bounding box of the new composite path. The composite path can now edited as a rectangular object with the Object tool. If you edit the composite path with the Reshape tool, you will be able to edit the subpaths (the former objects) in the composite path.
To split a compound object or composite path: Select the object
to split and choose Split from the Object menu. Any transparent holes will
disappear.