The image shows a sheep-pen, corral, or sheepfold in the Near-East tradition. The shepherd would lead the sheep into the pen at night. He would personally lay across the door of the sheepfold to keep the sheep in and to keep the wolves and other carnivores out.There might be many shepherds who could bring their sheep into the corral and share it. Each shepherd would gladly lay down his life for his flock, and might be found laying in the doorway. It is worth telling, each knew their individual sheep "personally" and by name.
In the morning, the shepherd would have his individual distinct call. All of his sheep would know this call. Contrary to the US where sheep are driven from behind with dog and mounted rider; in the Mid-East the shepherd goes ahead of the sheep and they follow him. Because, each one knows his master's voice.
John 10: 1-18, With a Focus on vv. 27-28
King James Version
27 My sheep hear my voice, and I know them, and they follow me:
28 And I give unto them eternal life; and they shall never perish, neither shall any man
pluck them out of my hand.
1 Verily, verily, I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber.
2 But he that entereth in by the door is the shepherd of the sheep.
3 To him the porter openeth; and the sheep hear his voice: and he calleth his own sheep by name, and leadeth them out.
4 And when he putteth forth his own sheep, he goeth before them, and the sheep follow him: for they know his voice.
5 And a stranger will they not follow but will flee from him: for they know not the voice of strangers.
6 This parable spake Jesus unto them: but they understood not what things they were which he spake unto them.
7 Then said Jesus unto them again, Verily, verily, I say unto you, I am the door of the sheep.
8 All that ever came before me are thieves and robbers: but the sheep did not hear them.
9 I am the door: by me if any man enter in, he shall be saved, and shall go in and out, and find pasture.
10 The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly.
11 I am the good shepherd: the good shepherd giveth his life for the sheep.
12 But he that is an hireling, and not the shepherd, whose own the sheep are not, seeth the wolf coming, and leaveth the sheep, and fleeth: and the wolf catcheth them, and scattereth the sheep.
13 The hireling fleeth, because he is an hireling, and careth not for the sheep.
14 I am the good shepherd, and know my sheep, and am known of mine.
15 As the Father knoweth me, even so know I the Father: and I lay down my life for the sheep.
16 And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one-fold, and one shepherd.
17 Therefore doth my Father love me, because I lay down my life, that I might take it again.
18 No man taketh it from me, but I lay it down of myself. I have power to lay it down, and I have power to take it again. This commandment have I received of my Father.