Reléguer (mettre) au second plan = To put into the background.

Planche

Faire la planche = 1. To show others the way; 2. To float on one’s back.

C’est sa planche de salut = It is his last hope, his sheet-anchor.

Plancher

Le plancher des vaches (fam.) = Dry land; Terra firma.

Débarrasse-moi le plancher (fam.) = Get out of my way.

Planter

Vous m’avez planté là = You left me without any warning; You left me in the lurch.