Q — Why do ordinands lie prostrate during part of the rite?

A — Prostration during the liturgy is placing oneself in a horizontal position before God.
To prostrate is to acknowledge the sheer reality of God as transcendent, to express one’s creaturely status, utterly dependent for life and grace from God.

So, for example, at the beginning of the Liturgy of Good Friday, the ministers also prostrate, expressing reception of the graces of the Paschal Mystery.

Prostrations are used during the celebration of Holy Orders, Religious Profession and the Consecration of Virgins.

In these contexts lifelong commitment is being expressed before the altar, which is a symbol of Christ.