This is what happened to me the other day. I had my sleeves rolled up. After reaching office I realized it was one of those shirts with cufflink holes and of course I left the cufflinks at home!
Step 1: Step 1 - Get a Clip
Easy fix, all you need is a U-clip! (or a 'paper clip' depending on where you live)
Step 2: Step 2 - Prepare
Fold the sleeve just as you would if you were to wear an actual cufflink.
Step 3: Step 3 - Through one side
Insert the clip through one side of the sleeve.
Step 4: Final - Through other side
Bring both ends close and secure the other side the same way.
Done! Go ahead and show it off!