Rigging: Part 2 - The mast at deck level

There are three basic types of mast locations: Keel Stepped/through deck, Deck Stepped located on deck and Tabernacle

Keel stepped masts travel through the deck and are normally sitting on a mast step located in the bilge. This type of mast must be centered in the deck with the old style wooden wedges driven in between the mast and the hole in the deck.  There are many different types of wedges including composite materials and on most modern boats a two part polymer which sets up semi-rigid and can be removed at a later date.  This junction between the mast and the deck should be checked periodically for corrosion, rust, rot and mildew which can damage the spar making this area the weak link in the rigging. This inspection should also include the mast boot.
Deck stepped masts sit on top of either the cabin top or the deck. This type of rig will have a compression post inside the cabin which should also be checked periodically for corrosion, rust, rot and mildew. The mast step fitting on top of the deck or cabin top should be thru-bolted and well sealed.  Special attention should be paid to stainless steel bolts thru-bolted through an aluminum deck step.  The only safe approach to inspecting these bolts is to remove and replace them and make sure they are of the same grade of stainless steel.  There have been incidences where the mast was swept from this fitting due to corroded stainless steel bolts which sheered under load.  Any and all attachments to this fitting should be checked for damage and inoperable shivs if applicable.
Any and all tangs, bails, bolts and rivets are subjected to very high load of stress in this area and is common to all types of masts.
Boom vang bails, cheek blocks and weldments should also be carefully inspected.  I strongly suggest removal of these items for inspection.   You can't inspect what you can't see.
Reefing hardware located on the mast is often overlooked and yet is just as important as the standing rigging.
Modern tabernacles are made of stainless steel and require the same maintenance and inspection as the previous types.
The pivot pin and locking pin should be inspected for damage and corrosion regularly.