What is a jumper cap and when do I use them?

[ArgonautQuest]

I recently ordered a PCB board kit. In this kit are some jumper caps as seen in this image:

I searched online but could not figure out exactly what these are. It appears, based on some articles I've stumbled upon like this one, that you close a circuit by pushing them onto some header pins. But why are some of my caps closed and some open as seen above? Can someone point me to a resource to learn what these are for and how to use them?

Thank you!

 

[bertus]

Hello,

Does the wiki tell you more?
https://en.wikipedia.org/wiki/Jumper_(computing)

Bertus

 

[hevans1944]

why are some of my caps closed and some open as seen above?

Often the terminal posts these shorting blocks are connected to are also test points. Leaving the top open for probing is a convenience. One very common application was using shorting caps to configure external disk drives as primary or slave drives, but this doesn't require access to the terminal posts covered by the shorting caps, so either open or closed works. Modern SATA drives don't need jumpers for configuration.

 

[Martaine2005]

Also, a lot of breadboard power supplies use shorting caps for choosing output voltage ie 3.3 or 5v.
I’ve always called them jumpers.
Cheap online DIY circuit kits like scopes, resistance decade boards and sig/func generators have them for changing values.



Martin