Utility Knife
Artifact — Equipment
When this Equipment enters, attach it to target creature you control.
Equipped creature gets +1/+1.
Equip 
(: Attach to target creature you control. Equip only as a sorcery.)
"Hold on a second, I have just the thing."
Craig J Spearing
Zendikar Rising (ZNR)
• #256Rulings
If the target creature becomes an illegal target, the Equipment remains on the battlefield unattached.
(wotc • 2020-09-25)
Attaching an Equipment with its enters-the-battlefield triggered ability isn't the same as using its equip ability. You don't pay mana for the attachment, and if the Equipment enters at a time you couldn't cast a sorcery, you can still attach it to a creature you control.
(wotc • 2020-09-25)
Rulings
If the target creature becomes an illegal target, the Equipment remains on the battlefield unattached.
(wotc • 2020-09-25)
Attaching an Equipment with its enters-the-battlefield triggered ability isn't the same as using its equip ability. You don't pay mana for the attachment, and if the Equipment enters at a time you couldn't cast a sorcery, you can still attach it to a creature you control.
(wotc • 2020-09-25)