The photo you've posted doesn't provide a clear picture of what you're doing or need. You appear to require the four guide pins that sit on the inside face of the quick-deploy rail kit. There are EIGHT per rail arm (for 2U and bigger servers. FOUR per arm on 1U systems). The only reason these would ever be removed is if the rails were installed in a 4-post threaded round-hole rack.
You haven't given good context on what you're trying to do, so that's why you haven't had good answers... It leaves us guessing... Why are the pins missing?
- You broke(?) the existing pins and you need one or more. Call your server vendor and describe the part you're looking for.
- You're missing a lot of the screws because someone removed them. Buy some used rail kits or go back to whoever sold you the equipment.
You can refer to these as "guide pins" and obtain them from HP, an HP vendor, or a used-server parts dealer if you need them.
Edit: They're definitely called "Guide Pins". See the HP video.