Assemble is related to Required. Required is related to Duty. Duty is the opposite of Voluntary. 
you are likely to find Stove in/at/on Apartment. you are likely to find Toilet in/at/on Apartment. you are likely to find Toilet in/at/on Trash. 
Assemble <--RelatedTo--> Required <--RelatedTo--> Duty <--Antonym--> Voluntary 
Stove --AtLocation--> Apartment <--AtLocation-- Toilet --AtLocation--> Trash 