The ladder's shape and the stone as temple and gate
Eustathius is explaining how the details of Jacob's vision and pillar at Bethel prefigure Christ, the cross, and the church.
So if we think about it, we can see that some people sometimes call the very sufferings of temptations by the name of steep rugged ascents and descents, paths with cliffs on both sides. Yet in shape the ladder does in some small way resemble the cross, fitted together with upright and crosswise timbers. When Jacob had beheld this vision, he took the stone on which he had reclined his head and rested, and he set it up as a pillar as a memorial of the event. He also made it an image characterizing the person who had appeared to him, and in it he established a renewal of remembrance. By calling it the house of God, he was hinting at the temple of God's Word, as the Son of the Almighty himself declared: "Destroy this temple, and in three days I will raise it up" (John 2:19). He also named the same stone the gate of heaven, because through the temple-building of Christ we are cleansed in body and soul, and so we are able to approach the divine nature.
Greek
Ἔστι γοῦν ἐννοοῦντας ἰδεῖν ὅπως ὀνόματι μὲν αὐτὰ τὰ τῶν πειρασμῶν πάθη κλιμακτῆρας ἔσθ' ὅτε κικλήσκουσί τινες ἀμφικρήμνους
ἀναβάσεις ὑπεμφαίνοντα καὶ καταβάσεις, σχήματι δὲ τῷ σταυρῷ προσέοικεν ὀλίγως πως ἡ κλῖμαξ, ὀρθίοις τε καὶ πλαγίοις ἁρμοσθεῖσα ξύλοις. Ὡς οὖν ἱστόρησε τὴν τοιαύτην ὀπτασίαν, τὸν λίθον ἄρας, ἐφ' ᾧ τὴν κεφαλὴν ἀνακλίνας ἡσύχασεν, ἔστησε μὲν αὐτὸν εἰς στήλην ὑπόμνημα τῆς ἱστορίας, εἰκόνα δὲ τοῦ φανέντος αὐτῷ προσώπου χαρακτηρίζων, ἐν ᾧ μνήμης ἀνανέωσιν ἵδρυσεν, οἶκον δὲ Θεοῦ προσειπὼν αὐτὸν, ᾐνίττετο τὸν τοῦ Θεοῦ Λόγου ναὸν ὡς καὶ αὐτὸς ἐξέφηνεν ὁ τοῦ Παντοκράτορος Υἱός· λύσατε τὸν ναὸν τοῦτον καὶ ἐν τρισὶν ἡμέραις ἐγερῶ αὐτόν. Ἤδη δὲ καὶ πύλην ὠνόμασεν οὐρανοῦ τὸν αὐτὸν, ἐπειδὴ διὰ τῆς τοῦ Χριστοῦ ναουργίας τὸ σῶμά τε καὶ ψυχὴν καθαριζόμενοι, τῇ θείᾳ δυνάμεθα προσιέναι φύσει.