I've used velcro or cordage with jammers for many of the smaller things … but the bilge-boards are more difficult.
Ideally a small spring loaded stainless bolt on the underside of the board slotting into a hole or hasp in the bilge-side … with finger access through a small hole to undo.
The stuff in the bilges really needs securing anyway … especially if it's that few dozen bottles of priceless champaign,
rum or brandy you are saving for a special occasion. Webbing straps attaching to shaped battens glued or glassed to the
bilge floor
work well … just be sure to leave drainage slots under them so the area between them doesn't become a secondary
bilge water trap.
Don't stop at the obvious cupboards, draws and bilges though … there are lots of things that need securing if you anticipate real rough
weather.
Companionway hatch and wash-boards should definitely be able to be secured and released from inside and outside. They also need a way of being secured when open or stowed. The lid of the chart table and
stove, fridge and basin covers are often forgotten about. Ideally, all the bottles, cans, boxes, tools, spare
parts and whatnot that accumulate in lockers and the lazarette should be secured …ditto the
anchor, spare anchor(s) and chain. Again, I tend to vote for webbing straps with glued or glassed securing points.
Even some of the things that look like fixtures may not be securely held in place if you anticipate extremes like knock-downs or (heaven forbid) roll-overs. A lot of fixtures are securely held 'down' … but might not cope too well when they need to be held 'up'.
Don't stop with below decks … topsides need checking too. On a lot of boats the
winch handles slot into little pouches … and will come out and fly around and get
lost in a knock-down or roll-over.
Cockpit lockers need securing (as in held down and up) to keep them closed at any angle.
And if you are in the habit of carrying a lot of paraphernalia on
deck … surfboards, sailboards, bicycles etc. think about what will hold them in place at extreme angles.
Of course, I have to admit to not always practicing what I preach … where's the fun in being perfect?
Happy Sailing.