We wanted our indoor cat to enjoy the outdoors safely. The leash/harness attempt was a total fail.  The smallest mesh pet pen works like a charm.  I bring him out on our deck in the morning while I have my coffee.  He enjoys watching the birds and squirrels in our back yard.  He use to paw at the slider begging to come out.  Now he can be with me.  I love that it folds up to the size of a dinner plate!