berkley quick release. $12 each. ihave 7 mounted on my boat. they come with 3 different mounting setups. the base shown in pic can be mounted 2 ways. like shown or like i done mine. i drilled a 1-1/8" hole in the top of the boat side and flush mounted the base by turning it over from shown in pic. then when the holder itsself is removed the base only sticks up 1/4"inch. flush mounted. and also comes with rail mount. i have rails on the bow of my boat. and i mounted 4 of the rail blocks in the front. 2 each side so i can swap them from the starboard and port sides.
i have a fish and ski so when were just boating or playing in it i can remove all the rod holders so your not catching your self on them and scratching yourself.
i dont like holders that you have to do the up and forward motion to get rod out. these have a steel arm that runs through top and hods rod in. but when a fish hammers rod all i have to do is grab the rod from either the front handle or rear and lift it straight up. no forward motion to get the rear of rod out. this is the style i liked best. plus the star knob on the right allows you to loosten and raise and lower the tip of rod up and down at any angle.
other pic shows the rail mount block.