When you adapt a geared bike to single speed, and strip it down to one ring at the front, you will find that the bolts are too wide to hold down the ring onto the crank. What you need is these skinnier ones.
6.5mm single speed only
Fed up with creaking bolts ?
These high quality bolts are super strong
Stainless so less likely to rust
Set of 5 bolts (you get one spare if you run a four bolt crank)
Stainless Steel Chainring Bolts for Single Chainset