Some days it's too wet to get outside on real rock and some days climbers just can't make it to the crag. Some are lucky enough to live near craggy hotspots but even then it can be hard to fit work, family life, and climbing into a single day or weekend. The indoor climbing gym is always an option but if you've got sturdy doorframes you can also hang fingerboards and bring the gym into the house.
Metolius Screw-On Handholds-10 Pack SCRE110
Metolius Greatest Hits Bouldering Set BOUL312
Metolius Screw On Rails RAIL103
Metolius Greatest Hits: Super 7 Pack Climbing Holds SUPE307