Trine forward immersion is the practice that gave the Brethren their nickname of Dunkers or Tunkers, from the German tunken, to dip. The candidate kneels in the water and is pressed forward three times, once for the Father, once for the Son and once for the Holy Spirit, on the grounds that Matthew 28:19 names three and that a person kneeling bows forward rather than falling back. Immediately after the third immersion, while the candidate is still kneeling in the water, the minister lays on hands and prays. Where there is a river the baptism happens outdoors; congregations without one use a baptistry. The practice was one of the boundary markers in the nineteenth-century arguments with the Baptists, who immerse once and backward.