Sash locks are one of the simplest types of hardware that could be used to lock a day bed and trundle bed together. They are the type of lock commonly used on many types of windows. Sash locks feature two sides; a catch and a tab that slides beneath the catch to secure the window. The tab on a sash lock is usually shaped like a half circle, but may also feature square edges. The appropriate shape will depend on how much mounting space is available on the bed frame.
Examine the bed frame where the trundle and day bed meet. Look for a flat area large enough to mount the sash lock and note the measurements. Measure the thickness of the frame and take the measurement into consideration when choosing mounting screws. Make a rough sketch of the area and take it to the hardware store. Examine and measure several types of sash locks and choose the best option based on the style and construction of the beds.
Measure and mark at least two level, equally spaced spots along the edge where the two beds meet. Hold one side of the sash lock up to the day bed frame. Mark the screw holes. Mount one side of the locking hardware with mounting screws of an appropriate length. Line up the second side with the first, ensure that the lock will engage properly and mark the holes for the second side of the lock.
The trundle bed must be pushed all the way beneath the day bed in order for the sash lock to work properly. The tab must line up perfectly with the catch. Once installed, simply rotate the tab until it engages and slides beneath the catch. If using a keyed sash lock insert the key and twist until the lock engages. Spray silicone-based lubricant into the keyhole if the key begins to stick in the lock.