During niddah, the couple may not sleep on the same bed – even if they are clothed, use different blankets, and do not touch.
Therefore, most couples have two beds that can be brought together when relations are permitted and separated when they are not. These beds should not touch when the couple is using them during niddah.
Couples who want to share the same large bed when the wife is tehorah may choose to keep an additional bed, or a trundle or sleep couch, alongside the main bed for one of them to use during niddah.
Although there is no absolute halachic measure for the distance between beds, some authorities require the beds to be far enough apart that the bedding does not touch, while others require that they be an arm's length apart.
As long as the beds come apart, and movement on one bed cannot be felt by someone on the other, the beds can be attached to a single headboard or footboard.
Using the Spouse's Bed
A husband may not sit or lie down on his wife's bed while she is niddah. According to some authorities, he may sit on her bed in her absence.
A wife may sit on her husband's bed, and lie down on it when he is absent, but she may not lie down on his bed if he is present.
(Restrictions on making each other's beds are discussed in Affectionate Service.)