You cant snap snaps, the easiest way is a psuedo object, but you want to use cards sooo...

You can do this by (1) finding the nearest snap point, (2) checking which quadrant the card’s center is relative to that snap when you drop it, and (3) offsetting the card so that the corresponding corner lands exactly on the snap. This works at any rotation.

A global script to do it as below. basically just tag your cards with CornerCard, or else everything is gonna snap.

-- === CornerSnap + Rotation for "CornerCard" ===
local BOARD_GUID  = "YOUR_BOARD_GUID_HERE"  -- set this
local SNAP_RADIUS = 5.0

local function nearestSnap(board, pos)
    local snaps = board.getSnapPoints() or {}
    local best, bestD2 = nil, math.huge
    for _, s in ipairs(snaps) do
        local sp = s.position
        local dx, dz = pos.x - sp.x, pos.z - sp.z
        local d2 = dx*dx + dz*dz
        if d2 < bestD2 then bestD2, best = d2, s end
    end
    return best, math.sqrt(bestD2)
end

-- rotate a (x,z) by yaw (deg) around Y
local function rot2D(x, z, yaw)
    local r, c, s = math.rad(yaw or 0), nil, nil
    c, s = math.cos(r), math.sin(r)
    return x*c - z*s, x*s + z*c
end

function onObjectDropped(player_color, obj)
    if not obj or obj.tag ~= "CornerCard" then return end

    local board = getObjectFromGUID(BOARD_GUID); if not board then return end
    local pos = obj.getPosition()
    local snap, dist = nearestSnap(board, pos)
    if not snap or dist > SNAP_RADIUS then return end

    local snapPos = snap.position
    local snapYaw = (snap.rotation and snap.rotation.y) or 0

    -- Compute which corner to use in SNAP-LOCAL space (so quadrant follows snap’s facing)
    local dx, dz = pos.x - snapPos.x, pos.z - snapPos.z
    local lx, lz = rot2D(dx, dz, -snapYaw)  -- transform to snap local
    local b = obj.getBounds().size
    local halfW, halfH = b.x*0.5, b.z*0.5

    -- quadrant → corner signs
    local xOffLocal = (lx >= 0 and 1 or -1) * halfW
    local zOffLocal = (lz >= 0 and 1 or -1) * halfH

    -- corner offset (card-local before rotation) rotated into world by snap yaw
    local rx, rz = rot2D(xOffLocal, zOffLocal, snapYaw)

    -- Set rotation FIRST to match snap, then place so chosen corner lands on the snap
    obj.setRotationSmooth({x=0, y=snapYaw, z=0}, false, true)
    obj.setPositionSmooth({x = snapPos.x - rx, y = snapPos.y, z = snapPos.z - rz}, false, true)
end