Factorio Forums

Idea for Factorio: Create snapping templates that by default or when a button is pressed (depending on how you have it configured) will always snap an object in the same location next to another object.
Example: snapping lamps to the left side of of power poles when placing lamps. You could run a line of power poles using the auto spacing (love that by the way) and then go back and hold down control or something and place lamps on the left side directly touching the power poll with the same running click motion of placing spaced poles because the lamps would all snap to that one location when its available. This would save time hand placing things (especially things that wouldn't work well with blueprints), and keep your factory uniform throughout (no more forgetting that you were putting the lamps at the bottom and then start putting them on the side and have weird meet ups.
Could also work with power lines two spaces above rail lines or other things that you try and keep uniform through the base.

Look up all the options with blueprints, you'll find what you're after.

I'm pretty sure what you described can't / won't be added as is with any entity, and the game just guessing what entity should be the one to be used for snapping.
But maybe could this be moddable, with an entity designed specifically for the purpose of blueprint snapping, forcing the game to place blueprints with that entity on top of that entity only.

Also, take note that this grid alignment/snapping feature will get improved when 2.0 is out : https://factorio.com/blog/post/fff-404. So still no auto-snapping to an existing entity, but "easier snapping to where one wants on the fly".

What if entities or parts of the blueprint could be tagged as "anchors"?

When placing a new factory my workflow is often:

1. Copy/make blueprint of two factories even though I only intend to place one.
2. Align with existing factory.
3. Place blueprint.

All the information is there. The game just needs to grab it and use it for snapping.