This model will test:

Z offset

Bed Cleanliness

First Layer Flowrate

First Layer Speed

Bed Temp

Round and Sharp Corners

Gapping

Bed Adhesion, and more!

I use this on my Neptune 4 to insure I have good settings, before committing to a long print. This reduces chance of the famous “Blob of Death” This is a great model to test first layer infill speed and line speed. It only takes 2-3 minutes.

Troubleshooting:

Nothing is sticking and it looks like spaghetti = Your nozzle is too high. Lower your nozzle (Z offset) Check Image Below

The straight lines are sticking, but not the round ones. = Clean you bed, and if issue persists, lower your nozzle (Z offset) Check Image Below

Every line stuck down, but the infill looks horrible = Your nozzle is too low. Raise your nozzle. (Z offset) Check Image Below

Every line stuck down, but there are significant gaps in the infill = Your nozzle is too high. Lower your nozzle. (Z offset) Check Image Below

Tips: 

Clean your bed every 10-15 prints.

Don't touch your bed with your fingers or any oily substance. Pick it up at the edges to reduce this.

Use a scrapper! I like ThreeD Michaels's scrapper (https://www.printables.com/model/832209-optimized-bed-scraper-xl). If you want a gridfinity holder for it, check here → https://makerworld.com/en/models/1181792-optimized-bed-scrapper-xl-holder

Lower your first layer speed. Anywhere from 40-60mm/s is good.

I hope this model and these tips will help you, If so, please drop a boost or a like!