knit

2. VERB

If someone or something knits things or people together, they make them fit or work together closely and successfully.

• The best thing about sport is that it knits the whole family close together.     
• Ordinary people have some reservations about their president's drive to knit them so closely to their neighbors.

Knit is also a combining form. COMB in ADJ : usu ADJ n 

• a tightly knit society.
  

..... Cobuild

tight-knit: closely and firmly integrated; "a tight-knit organization"  = tightly knit.