The central observance of Holy Thursday is the ritual reenactment of the Last Supper at Mass. This event is celebrated at every Mass, as part of the Liturgy of the Eucharist, but it is specially commemorated on Holy Thursday.  

Also, during the Mass on Holy Thursday, the establishment of the priesthood is reenacted with the priest washing the feet of several parishioners.  
 
At the end of the Holy Thursday Mass, the Body of Christ is brought in procession to a temporary "Altar of Repose" away from the sanctuary. It is customary for the faithful to process together to this altar and spend time in quiet prayer and adoration.