One of the most frustrating parts of building a printer with 1515 extrusions is the need to pre-load nuts, and inevitably forgetting (multiple times... or was it just me?) to pre-load nuts in the right place.
These only work in LDO frames
Finally (with a capital F like 10 times) there are nuts you can slide in your extrusion. Here they are :). Comes with 20pcs.