double-lock

[ duhb-uh l-lok ]

/ ˈdʌb əlˈlɒk /

to lock with two turns of a key, so that a second bolt is engaged.

to fasten with particular care.

Origin of double-lock

First recorded in 1585–95

Then he left the closet, taking care to double-lock the door.

The Exploits of Juve |Pierre Souvestre and Marcel Allain
The single-lock and double-lock bridges with two and three spans of 15 ft., respectively, are the ones of most utility.

Manual of Military Training |James A. Moss
You will be at liberty to double-lock my study door; you can go to sleep without the slightest fear.

My Neighbor Raymond (Novels of Paul de Kock Volume XI) |Charles Paul de Kock
And with that she blew him a kiss from the threshold of her bedroom, and Rudolf heard her double-lock the door behind her.

A Hungarian Nabob |Maurus Jkai

I got up, with a shiver, to shut and double-lock it; then I made for the alcove, and went to bed in haste.

An "Attic" Philosopher, Complete |Emile Souvestre