What happens to the chains and downs box at the end of the 1st and 3rd periods?

The teams change ends at the end of the 1st and 3rd periods. At the start of the 2nd and 4th periods the ball is put into play at a point corresponding exactly to where the ball became dead at the opposite end of the field, in the same manner as if play had not been interrupted.

The Down Judge is responsible for changing the position of the distance chain at the end of the 1st and 3rd periods to the identical spot, at the opposite end of the field, corresponding to the point at which play ended in that period. The downs box and distance chain stay under the direction of the Down Judge, and out of bounds.

Source: Canadian Amateur Rule Book for Tackle Football 2026-2027, Rule 1 Section 3 Article 3, Rule 2 Section 7 Article 4(c), and Rule 2 Section 10.