add_exit
adds the room exits
int add_exit(string direc,mixed dest,string type,string material)
eg add_exit("south","pathtonestroom","door");
valid exit types are:
   "standard"
   "corridor" 
   "plain"   
   "door"     
   "stair"    
   "hidden"   
   "secret"   
   "gate"    
   "road"     
   "path" 
Don't use anything else :)
There's also add_dig_exit to add exits that have to be uncovered.
See also renew_exits if you do anything cute with adding/removing exits