Rattus makes great points.
If you have doubles, you can use them for assistance work as a part of 5/3/1.
Take the Military Press for example, you can do double military press.
Or use Double Kettlebell Front Squats
Also you can use them for conditioning workouts. Winter is coming here, and with the ice and snow, I'm less likely to to sprints outdoors.
Take a kettlebell, swing it or snatch it, then put the bell down and jump rope. Alternate between the 2 for 20 minutes.
On De-load week, I used strictly kettlebells to recharge and had really good success.