Steve you inquired of me as to secret compartments. Yes over the years I have built several from hidden gun rooms in homes to hidden safes and vaults under stairways. In cabinets I have used the toe kicks under cabinets to make hidden pull outs. I have hidden compartments behind drawers using full extention slides and stop the drawer short enough to hide the fact that there is a void behind the drawer. To access it you have to remove the drawer. I have made hidden compartments behide the actual face frame of which is hinged to drop down after moving a latch. In these I use a wide upper top rail. You can do the same thing in furniture. In tables I have used the center post or pedestal of which I have made it in a mission style and leave the pedestal open sometimes making is as big as 10 to 12 inches and make a section open by pulling off a side much like a box lid. I hold these on using friction balls. In bed frames posts of mission style and some stair banister I have left the post centers hollow and accessing it either by a removable side or leaving the top cap removable. (note on stairway post do not use a post where it is often pulled on, leaned on, or handled much as it will get loose and easily found) Use a post that is either attached to a wall or otherwise not handled much. Hole the post caps on using friction balls and make the cap tight. Hide the joints using moldings.
In fireplace mantels use the top as a hidden compartment that has a hinged top with the hinge hidden. I have used European hinges for this. In top cabinets that are held againt an interior wall the cabinet can be made to be removable revealing a entire open framed in wall cavity. Large hidden compartments can be made in the tops of cabinets or furniture using tall crown moldings and putting a false hinged top. Hinged bookcases that are either have the build in look or the ones that appear to be mounted to a wall also make excellent hidden voids and even rooms These are secured by hidden pins that are even lockable for family members (juneniles that you do not wish them to access.)
One of my favorite places is in basements of which I helped build a room about 10 x 12 feet of which held a large collections of guns, cameras, coin and jewelry safes and art work handing on the wall. It had a climate controlled system in it and was hidden by a large sliding shelving system that was suspended from above on large barndoor tracks of which was hidden by the ceiling system. It was locked by a sliding bolt system that was hidden behind the faceframe of the shelving system casework and dropped down into the cement floor and up into the upper cement foundation system. (continued)
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In all these cases it is best to add more security such as alarms and cameras and above all do not discuss this with any one if you expect to keep it a secret feature in your home.
In my years of being a cop I have seen many hidden compartments from the normal hole in the wall and floor of which is hidden by a hanging picture and a piece of furniture sitting over the floor opening. Things like light switch plates, toilet tanks hidding things like drugs. Ceiling duct work and false ceilings and other construction voids have been used to hide contraband. One of the favorite of "crankers" is diaper pails as it is a perfect place to hide the drug. It is disgusting to handle to most yet has odor masking trends to hide the drug, (crank smells alot like urine) You could expect to find contraband in dog food sacks dirty clothes hampers, freezer compatments. Holes were often use to hide items in cans jars and plastic were common.
One of the most surprising one is a false plumbing pipe that was 4 inch in diameter and capped on each end with one end, being the top left unglued. It was in a closet and extended from a hole in the floor that was cut through the top underlayment and floor carpeting and resting on the sub-floor. It continued up through the ceiling and was accessed by liting the pipe up and pulled outward through the closet door. The large hole at the top was hidden by a piece of sheet metal cut to where it would slip down the pipe as you lifted it upward. The pipe would slide up into the attic insulation, That way it was not visible from the attic as it was covered by the heavy layer of insulation and not visable from the crawl space under the house as it didn't go through the floor. It contained a vass amount of drugs and money. These also had their security apart from the normal that we use but by dogs, and trip wires sounding things from ratteling tin cans to actual explosive devices. There was the things like using the gasoling bombs of which had two things in mind to protect themselves by preventing the discovery and or getting rid of the snooping person and also to destroy any evidence. This worked by using a large light bulbs of which an acetylene torch was use to melt a hole in the glass bulb. It was filled with gasoline and the hole plugged by a putty or a pice of tape. The bulb was screwed back into its socket and just set there waiting for the opening of the closed door and the flip of the electric switch. The closet became an instant fire bomb and halted most operations in discovery of the items of contraband. The also used the fear tatic to great advantage. Lots of fun and an life lasting experience too.
Anyone have a cyclone fence that fences off the back yard? Want to hide a key to your home? Don't use a key under the mat, in the mail box or under a rock or flower pot. Don't even use the key over the door either. It is too common and is easily found. It is like leaving your garage door opener in your car and it parked outside. One of the best methods to date is use of the fence. Remove the rain cap from a post. glue in a small piece of wood to the inside of the cap. suspend a key on a nylon fishing line from the wood in the cap down the fence post. Replace the cap and no one unless you tell or allow some one to see you will know your hidden key location. Hidden key vaults are not good either as they are easily found. Have a great day