You can use various barriers and techniques. Here are some ideas:

Clear Burglar Bars: Clear Burglar Bars can be used to act as barriers to keep cats indoors, as long as the spacing between the Bars are done in such a way to prevent cats getting out. These Clear Bars also adds to the security of your home.

Window Screens: Install sturdy screens on windows to prevent cats from escaping through them.

Balcony Nets: If you have a balcony, consider installing a net or mesh to enclose the space and prevent cats from falling or jumping off.

Cat Enclosures: Create an outdoor cat enclosure or “catio” that provides a safe outdoor space for your cats without the risk of escape.

Fencing: Ensure your yard is securely fenced to prevent cats from wandering off.

Door Barriers: Use door barriers that cats cannot easily push open to prevent them from sneaking out when doors are opened.

Supervision: Always supervise your cats when they are outside, and bring them in when you are unable to watch them.

Training: Train your cats to respond to recall commands, so they come back inside when called.

Remember, the safety of your cats is paramount, so always prioritize secure barriers and supervision.