dam, jock, inclined plane on a canal, where boats can be hauled up or down
埭 centers on a barrier or slope for controlling water and moving boats: a dam that holds water back, or an inclined plane on a canal where boats can be hauled up or down.
埭 combines 土 (earth) with 隶, which likely contributes the sound. The character refers to an earthen dam or canal slope, fitting the earth radical.
The earth radical 土 on the left suggests a structure made of soil. Picture a raised earthen bank (dam) or a sloped canal wall where boats are pulled up.
For タイ, imagine a boat being tied to the dam before being hauled up the slope: tie -> タイ, and the earthwork holds the water back.